pfi TEACHING APPLIED ELECTRICITY Thesisfor Degree of E. E. George A- Willoughby . V . 1 . . E...o. -.sotn . .. ... ¢.A£o.co..os¢olo.. ‘4 .~ .ocoo..ov¢~ ‘QOO.O..O.6,o..¢.btn‘oo.v.‘nu on..oo.>.&§..o...... 9. . o o I . ...o o u. n... v.0.».0..b~c~l.. ..I . no. . ...u Igodo‘-.- o.~ 9 ¢¢.o.o..oo o o v.o ...... vaoOooIQQOQO...OOIA. AOI O . ubottol..lnt .. .n. o .ov.o\. . 50‘ v...coo. . .9... ... .. .. . . I. .. .I-QOC. .Ioouo . o o 9 .0 3.0.4 3.3.0.. . TEACHING APPLIED ELECTRICITY A Thesis Submitted to The Committee on Advanced Degrees of The Michigan State College BY r 1: I . . , n George A. Wllloughby, B.S., lo Candidate for the degree of J ELECTRICAL ENGINEER ,3 I , THESIS PREFACE The exceptionally rapid advances made in the development of electrical power and in the manufacture of electrical devices have revolutionized, to a certain extent, the field of education in which electrical applications are covered. The development of electricity in the home, the numerous applications of electri- city in the automobile, and various other uses of this power have tended to create an interest on the part of almost everyone and also a desire to learn more and more about the subject of electri- cal applications. This extensive development has broadened the field of edu- cation along electrical lines and has necessitated many additions and changes. In the past, the study of electricity has been con- sidered largely from a scientific standpoint. Now the study of applied electricity is valued by many classes of peOple and subjects of this nature are being rapidly introduced into curricu- la of a great many educational institutions. These institutions include public and private vocational schools, technical schools, and others. In fact, it is not at all uncommon to find electrical work given in the upper grades, in classes for girls, and in nmny other classes below college grade; and it is not uncommon to see ”electrical home" demonstrations and the like for the purpose of assisting the general public in becoming more familiar with the wonderful possibilities in the deve10pment and use of elect- 10-1 .1 143 rical appliances. The work of organizing educational material and presenting this material to the various types of classes and to people in various walks of life is of no little significance. There are many problems which are still far from being solved. The field is so broad and so many different types and classes of peOple' are interested in the work that it is doubtful if any one person or group of persons can expect to accomplish everything that may be accomplished along this line. Never-the-less some progress has been made. Some nine years ago the work of deve10ping courses in prac- tical electricity was assigned to the author in addition to that involved in teaching the subject as a science. With very little available material at hand, an attempt was made to do this job satisfactorily. The work is still unfinished but there is some satisfaction in the fact that material has been produced in the form of text books, instruction sheets, and other teaching devices which are now being used in hundreds of schools; and that thru personal contact with members of all-day and evening vocational classes and in industry, a great many people have been assisted in entering or advancing in the great field of electrical work. In more elementary classes, peOple have been taught to make proper use of the many conveniences available thru the use of electricity. In the following material, special emphasis has been placed uPonthe thoughts brought out in the development of practical rather than theoretical work which has been commonly given for many years. It is hoped that these thoughts will reflect certain possibilities in the way of content of courses or methods of instruction which will be of value to others who are engaged in, or entering upon, this kind of work. Saginaw, W.S.,Mich. George A. Willoughby. TYPES 9E COURSES l§_APPLIED ELECTRICITY There are a great many types of classes in which some phase, or phases, of applied electricity may_be taught. In fact, one particular subject such as motor work may be divided into several different classes. It is the intention at this time, however, to limit the discussion to the various types of instruction, or courses, rather than individual classes under any_particular head. Typgg 3; Courses. Some of the types of courses most commonly found at the present time are the following: Household Mechanics . Elementary Construction 1 2 3. Tryout or "Finding" 4 General Manual Training 5. Elementary Technical or Scinktific 6. Elementary Vocational 7. Vocational 8. Technical Household Mechanics. A type of course commonly called "household” mechanics" is one in which the aims are largely to teach simple use and repair of electrical devices about the home or in every- day life. Some of the jobs included in such a course are repair- ing, or making up, a heater Cord; making up an extension cord for a lamp; locating a blown fuse and replacing it, locating a short —w ---- - - —--~—_‘—-- ~ "..~. Exam :1ng §E;:;J=.=1.'~. .‘u Fug-.2112: '40 TEX .C .Wflq 30105 “010.3; at {-L~+l..'3,p_. 'J '10 f. 'i‘é'j $11."le 35°71!) B. 9‘18 9193'? she ,3oxl nI’ .ddgsui ad gem nainx.:eois heiiqns lo ,eaaan w _.. I“: .‘C '- LB'I‘W” OJ“ 1'95”“! ‘50 DYE?" 3131"“ H-JW’I . 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In many cases, jobs of this kind have been given in the seventh or eighth grade. This has been Justified by the fact that a great many pupils never enter high school or other institutions of higher learning but must enter upon their life's work at an early age. Thus the instruction in the grades should be as pract- ical as possible. Elementary Construction. Work of an elementary construction nature has been given in many elementary classes in the grades and high schools. It may even be carried into the college or university. This kind of work consists chiefly of making devices from simple toys to those which compare quite favorably with commercial products. In the most elementary classes, toy motors, simple magnetic devices, simple heaters, and the like have been constructed. In the more advanced classes, devices of a similar nature but of larger capacity and of more intricate parts may be built. ‘ Elementary construction is justified in that it creates a great amount of interest on the part of the pupil and.1t teaches the parts and construction of devices to such an extent that applications of similar parts in commercial devices will be much more readily understood. The chief disadvantages of this kind of work are that a large number of materials and tools are required and the time necessary for making the device may be too great to Justify omitting other things which might be given in the same period of time. .931; ”JJ .xm .ncw; J?Ltt.8 gr .arfixa 1n typd T9HJ1: biinfl( dnu" on zevi uu “PM a ‘ -31031 n) beiaéxédui sis Uh» fi‘EOd 31 a’uexfa If £58 * 1 133m HI .nxuw 119121 {suluJWMI1 aw; wiafij "n 9,03 2: anavaa 9&3 “I n9v.; na'n nv« ' Li: ”1“; 1. ’ 38911.; 3 3.6113 3031 13.;3 \,t- 3‘;G:'1;JLAJL,°‘.. 1.3‘ aid? 10 anoiausktami findéh '( Intann g;;u uajne tevu \ n3 J3 210w e'611"11~nj .r u w- . 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Work of a finding nature is given to pupils to help them to determine what particular line of work they may desire to enter as a vocation. It is intended to give them a working knowledge of the various lines and what the possibili- ties are along certain branches. Work of this kind may include some house wiring, some automotive electrical work, some motor maintenance and repair work, and the like. One of the chief aims is to permit the pupils to get “actual experience” such as they will get when they enter the field if they should find themselves adapted to any particular line. Tryout work is justified in that it assists in eliminating some of the cases where pupils enter upon a life work with no idea of what they are getting into; and also in that it helps pupils to avoid being forced into some particular vocation when they are much more adapted to some other line of work. General Manual Training. Under the head of manual training, instruction has been carried on in the public schools for years. Until comparatively recent years this was largely woodworking. The chief aims have been to teach the use of tools, care and accuracy, and to develop the creative instinct. Now electrical work is being given in addition to woodworking and the aims in- clude the foregoing as well as that of assisting the pupil in making good use of his liesure time. Electrical work in manual training classes includes many types of construction and repair. Where the aim has been what is often called “cultural" rather than “vocational" the con- struction of various devices including radio sets and the like has been carried out. Elementary Technical Work. Elementary technical work is that in which the chief aim is to teach the pupils many of the more elementary technical points involved in electrical devices and their use. It is more or less scientific in its nature. This type of work is justified in that it gives pupils fundamental information of a technical nature which will assist them in understanding reading matter and discussions of technicd. topics and also provide a basis upon which to continue further scientific study and application. Work of this kind has been given as science but it has been enriched by the construction of devices or by the study of com- mercial devices with the idea of learning how the scientific prin- ciples of electricity have been applied in them. Pupils are also given such work as takingxueter readings, determining power costs, etc. Elementagy Vocational Wg£k_. In many cases pupils enter industry with very few qualifications except those received in schools of an elementary type. They lack the broad foundation provided by high school courses enriched with vocational subjects. In fact, even at the present time, the percentage of grammar school graduates who enter high school is comparatively small and an exceedingly small number of those who enter high school ever get as far as college. Elementary vocational work has been attempted in many cases for the purpose of assisting these pupils who will enter industry instead of entering institutions of higher learn- ing. This type of work includes some of the more simple trade processes which one entering industry is most likely to be called upon to do. In the house wiring field, these processes may include making up fixtures and simple wiring. In the auto- motive field they may include taking batteries out of cars, dismantling batteries, clashing terminal posts,and the like. Vocational Work. Vocational work such as given in all-day, part-time and evening classes and schools is such as to prepare pupils to enter industry or to advance in industry if they are at work. The trade preparatory work especially is intended to prepare pupils to enter industry with at least a working know- ledge of most of the jobs involved in any particular vocation, and with sufficient skill to be able to do the work expected of an advanced apprentice or helper. This kind of work is intended to offer the possibilities of the old apprenticeship system which is now obselete in many places, and perhaps a greater opportunity for the advancement of the pupil and for acquiring required related work or technical knowledge. Technical Eggg. Technical courses are those of a scientific or engineering nature such as have been given in an elementary way in technical high schools and followed by courses in engineering schools and colleges. Work of this kind has been carried on for years and has established itself as fundamental. Never-the- less these courses may well be enriched by instruction some- what along the line of vocational work. A combination of theory and practice is best. II CONTENT 9}: VARIOUS TYPES pg; COURSES The content of a course,and the methods of instruction used depend to a large extent upon the aims and purposes of the course and the time devoted to the work. In planning a course, the aims should be carefully considered first. Just what is to be accomplished by giving the work? What is the student to gain? After the aims have been definitely decided upon, the next important question to consider is, What work and study may be included to accomplish the desired results? Then after a large number of tOpics or jobs have been listed which may logically be given in the course under consideration, the next question arising is, How much time is going to be available for present- ing the required instruction? If the time is very limited, it is necessary to employ methods which will relieve the pupils of all possible loss of time and even then it may be necessary to eliminate some of the less important parts of the course if sufficient time is not available for completing them in addition to those of major importance. Because of the variation of time allowances and the differ- ences in the aims of various courses, it is difficult to outline definitely just what should be attempted in any particular case and expect that to apply directly to every other case. However, it is possible to list some of the things which may well be in- cluded in courses of variOus types as an aid in deciding definite- ly upon the content for any individual case. If possible, it is well to procure an analysis of work such as given under the 10 head of Vocational Courses. Content 3; Household Mechanics Course. In a large number of cases, the time devoted to household mechanics in perhaps the eighth or ninth grade is limited to one period a week for forty weeks and the portion devoted to electrical work may be limited to ten periods. It is evident that if this is the case, the content must be very limited and the time must be conserved as much as possible. The content of a course of this kind may be such as follows: 1. Dismantle, repair and assemble a heater cord extension. 2. Dismantle, repair and assemble a lamp extension. 5. Test and replace fuses. 4. Test for and remove a short circuit. 5. Remove, repair and re-install a flush switch. 6. Remove, repair and re-install a flush receptacle. 7. Remove, repair and re-install a snap switch. 8. Read a kilowatt-hour meter. 9. Remove, repair and re-install a drop cord. 10. Make simple bell installations. If time permits, additional jobs of a similar nature may be given or it may be desirable to include some work which is not Strictly "household mechanics". Content 2: Elementary Construction Course. In a course of the elementary construction type the time may be very limited or the course may cover a period of a semester or even a year or more. Thus the content of the course will vary greatly in individual cases. Since in construction work the principles Of electricity 11 are applied in practical ways, it is well if time permits, to include considerable of what might be termed experimental material to show the pupils the principles applied in the devices they are constructing. If the time is extremely limited, it is possible to furnish details of a device and permit pupils to construct it without taking up the technical or scientific study of the principles involved. That is, pupils may be permitted to make a heater without studying the heating effect of electricity, resistance, etc; and they may be permitted to make small motors without studying the principles of magnetism, induction, and the like. If possible, however, it is well to connect the theory with the practice by giving experimental work in connection with the construction. The content of a course of this kind may include: 1. Making a toy motor. 2. Making an electric stove or other heating device. 3. Making a simple radio set. 4. Making a transformer. 5. Making a rectifier. If some experimental work is given, and other work of a nature that will help the pupil understand principles, the purchasing of materials and the like,the following may be included: 1. Testing materials for their conductivity. 2. Learning the names and characteristics of materials. 5. Learning to use dry cells prOperly. 4. Learning how to use storage batteries. 5. Comparing resistances of different wires. 6. Connecting different devices. Content g£_§ "Finding? Course. Since one of the chief aims of a finding, or tryout, course is to give pupils an opportunity to determine whether or not they are interested in and adapted to a particular vocation, the content should be made up as much as possible of work similar to that found in commercial practice. In ‘House Wiring", the following may be included: 1. Making up a Simple Pendant Fixture. 2. Making up a DrOp Fixture. 3. Testing a Fixture for a Ground. 4. Installing the Wiring for a Ceiling Fixture to be Con- trolled by a Snap Switch. 5. Installing the Wiring for a Bracket. 6. Installing the Wiring for a Drop Fixture to be Con- trolled by a Flush Switch. 7. Installing the Wiring for a Flush.Receptacle. These jobs,and perhaps others, may be done by the various umthods such as knob-and-tube, BX or armored cable, and conduit. In ”Motor Work", the following may be included: . Winding Coils. . Taping Coils. Placing Coils in a Motor. . Testing a Motor for Grounds. 01erme . Replacing Fuses. "Automotive Electricity" work may include: 1. Cleaning the Posts of a Storage Battery. (0 . Removing Sealing Compound from a Battery. . Removing the Elements from a Battery. #03 . Testing a.Motor or Generator for Grounds. 13 5. Installing Spot Lamp or Stop Lamp. The jobs listed are but a few of those which may be given if time permits. If the time is extremely limited, special meth- ods may be used as explained later. Contents 9: General Manual Training Course. The contents of a general manual training course will depend quite largely upon the type of pupils in the class and the time devoted to the work. Many parts of other courses may be included such as those listed for an elementary construction class, a househOldmechanics class, a technical class, or a vocational class. In a so-called manual training course, many devices such as radio sets, lamps, rectifiers, motors, heating devices and the like may be constructed. ' Content 3; Elementary Technical Course. Since the aim in an elementary technical course is largely to give pupils a fundamen- tal knowledge of the principles of electricity and their appli- cations, a course of this kind may be somewhat similar to an elementary course in electrical science consisting of a series of experiments enriched if possible by the construction of simple devices and the study of commercial devices to assist the pupils in understanding some of the practical applications of the principles. . The following may be included in an elementary technical course: 1. A Study of Magnetic Fields; Making a Magnet 2. Induced.Magnetism; ExperimentSJand Making Induction Coil. 5. The Dry Cell; Making a Cell. 4. Study of Voltages and Connecting Cells. l4 5. Storage Cells and Batteries. 6.‘ Taking Electrical Measurements. 7. Ohmls Law. 8. Rectification of Alternating Current. 9. Charging Storage Batteries. 10. Heating by Electricity. 11. Generating Electric Current. 12. Expansion Due to Heat. 15. Fuses and How They Work. 14. Resistances. 15. Electric Lighting. Content 9; Elementary Vocational Course. Since the aim in an elementary vocational course is to give pupils training which will assist them in entering and making good in a vocation along electrical lines, it is evident that such a course should con- tain material which is as nearly as possible like that found in commercial practice, and the work should be as nearly as pos- sible like that carried on by tradesmen in the various lines. The content of a course of this kind may be made up of the more elementary processes involved in electrical vocations. It may be similar in many respects to that of a finding course if the time is limited, or it may be made up of the more elemen- tary parts of a strictly vocational course. The exact content will depend upon the age of the pupils and the time devoted to the work. An elementary vocational course may include the following: 15 House Wiring As much as possible of the vocational course on House Wiring. Motor Work As much as possible of the vocational course. Miscellaneous Work As much as possible of the miscellaneous work under vocational. Content pf Vocational Courses. Vocational courses are intended to give students actual trade training which will prepare them for trades or assist them in advancing in a trade. It is evident that vocational courses must contain practical work given under conditions as similar as possible to those actually found in industry. In any specific case, the work should be as extensive and as practical as possible. ‘ As the first step in determining the content of a vocational course, or any other in fact, it is well to make a careful analy- sis of the work. It is well to determine as definitely as pos- sible just what is most essential for one to know who is to enter any particular vocation. If this information is avail- able for use in arranging the work for a course, the work is simplified to a great extent and the content of the course is more likely to be satisfactory. An analysis of electrical occupations and of electrical processes or jobs is given in the following pages. The trade processes are arranged in instruction blocks, or steps. When selecting the content of a course of a given nature, blocks required for the given type of work may be selected and arranged in a definite order. For some courses it will be desirable to use only parts of some blocks. 16 E CTRICAL OCCUPATIONS _;._ Construction, Maintenance, Trouble-shooting and Repair Occupations. 1. OWNER Knowledge required: 1. Selection and specification of materials 2. General electrical construction 3. Wiring, code rules, electrical equipment 4. Estimating 5. Selling (if possible) 6. Book-keeping (if possible) II. WIREMAN Knowledge required; 1. Reading architects'blue-prints 2. General knowledge of electric circuits 5. Wiring methods 4. Code requirements 5. Selection and specification of materials 6. Knowledge of common electrical equipment 7. Repair and trouble-shooting (usually) III. ESTIMATOR Knowledge required: 1. Reading architects’blue-prints 2. General knowledge of electrical circuits 3. Wiring methods 4. Code requirements 5. Selection and specification of material 6. Knowledge of common electrical equipment 7. Mathematics 8. Drawing IV. SALESMAN Knowledge required: 1. Uses and applications of electrical equipment 2. Principles of operation of Fans Washing-machine motors Irons, heaters, etc. 3. Installation methods . Selection of materials .p. 17 V. GENERAL REPAIRMAN Knowledge required: 1. Electrical circuits. 2. Trouble-shooting 3. Repairing of all kinds of common equipment 4. Interior installations 5. Principles of operation of electrical equipment VI. MAINTENANCE MAN Knowledge required: . Broad diversified training Repairing electrical troubles Trouble-shooting Installation of electrical equipment Knowledge of equipment used in commercial or industrial establishments thCfiNi-J VII. ELECTRICAL INSPECTOR Knowledge required: 1. Extensive knowledge of electrical construction 2. Wiring methods 3. Knowledge of electrical equipment 4. Electrical troubles VIII.ARMATURE WINDER Knowledge required: 1. Electrical theory 2. Principles of generators and motors 3. Armature-winding experience 1X4 AUTOMOBILE STARTING AND LIGHTING SERVICE WORKER Knowledge required: . Technical knowledge of electricity . Automobile wiring . Automobile lighting Low-voltage generators and motors Trouble-shooting Repairing Principles of operation of common electrical accessories. thfibCflNl-J X. IGNITION SERVICE WORKER Knowledge required: 1. Principles of ignition 2. Practical knowledge of electricity 18 3. Terms, methods of generating and transmitting electrical current ' 4. Magnetos 5. Testing and adjusting ignition equipment XI. STORAGE BATTERY SERVICE WORKER Knowledge required: 1. Theory of storage battery 2. Storage battery troubles 3. Repairing of batteries 4. Charging batteries XII. MANUFACTURER OF ELECTRICAL EQUIPMENT AND DEVICES Knowledge required: General knowledge of electrical applications Principles of operation of electrical devices Complete understanding of electrical theory . Methods of manufacture 5. Production methods. hCflNl—J XIII. OTHER MORE SPECIALIZED WORKERS. ELECTRICAL WORK 19 Construction, Maintenance, Trouble-shooting and Repair CONSTRUCTION WORK Voltage less than 50 Bell work Annunciator work Burglar alarm work Special push-buttons (connecting) Dumb waiter work Other low-voltage electro- magnetic devices (connecting) Battery li hting Dry cells %connecting) . Special operations tOGDQ OthkCflNH Voltage more than 50 House wiring Assembling fixtures Conduit installations Metal and wooden moulding Sign work Motor installations Rheostat and starting box installations Switches and A.C. Starters Generators, switchboards, transformers, meters {0(1) QOUIrPCflNH MAINTENANCE , TROUBLE-SHOOTING , REPAIR Voltage less than 50 1. Dry cells 2. Storage batteries 3. Bell circuits 4. Bells 5. Annunciators 6. Special push-buttons 7. Dumb waiters 8. Other magnetic devices 9. Starting systems in autos lO. Ignition systems 11. Battery lighting Voltage more than 50 l. Heaters 2. Heater circuits 3. Lighting circuits 4. Small motors 5. Grounds 6. Motor circuits 7. Switches 8. D.C. Motors 9. A.C. Motors 10. A.C. Starters H H . Generators,transformers (Many other things being developed from day to day) II-c. III-C IV-c. VI-c. VII-c. 20. CONSTRUCTION BLOCKS; QR STEPS BELL WORK 1. Running wires 2. Installing bells 3. Connecting bells in parallel 4. Connecting push-buttons in parallel 5. Connecting several bells controlled by individual push-buttons 6. Bells and buttons, both in parallel 7. Connecting double-contact push-buttons 8. Installing a polarized bell ANNUNCIATOR WORK 1. Installing annunciators BURGLAR ALARMS Installing simple open circuit alarms Installing alarm window springs Installing door springs Installing door trips Installing closed-circuit alarms Installing floor treads Installing alarm.matting QO‘JCBthCflNP" SPECIAL PUSH-BUTTONS 1. Installing a portable push-button 2. Installing a paper weight multi-push desk button 3. Installing combination floor pushes 4. Installing a flush push-button DUMB WAITERS 1. Installing dumb waiters OTHER MAGNETIC DEVICES Installing a magnetic door Opener Installing relays Installing railway signals Installing furnace regulators Call-system signals . Fire alarm systems . Devices on automobiles QOEUIPOINH BATTERY LIGHTING Connecting battery lamps in parallel . Connecting battery lamps in series . Connecting a one-wire system . Connecting resistance in a circuit Installing battery switches 01¢me VIIILc. IXTC . XI-c. XII-c. 21. DRY CELL WORK hum?“ in series in parallel in series multiple in multiple series cells cells cells cells Connecting dry Connecting dry Connecting dry Connecting dry SPECIAL OPERATIONS 1. 2. 3 4. Making a tap Making a splice Soldering a joint Taping a joint HOUSE INSTALLATIONS (additions to installation) Connecting up a heater cord Connecting up an extension cord for lighting Wiring an electric lamp Installing a receptacle Connecting an additional lamp onto a circuit Connecting on a three-way switch arrangement Connecting on an extra switch. Installing a fuse block. Adding a wall bracket to an installation. HOUSE WIRING (Knob-and-tube tap system) 1. Wiring for a ceiling fixture 2. Wiring for a bracket 3. Wiring for a single pole snap switch 4. Wiring for a single pole flush switch 5. Wiring for a flush receptacle 6. Wiring for a gang of switches 7. Wiring for a set of three-way switches 8. Wiring three-way and four-way switches 9. Wiring for a double pole switch 10. Wiring for a door-jamb switch 11. Wiring for an electrolier switch 12. Wiring for a service entrance 13. Running in branch circuits l4. Tapping onto branch circuit wires 15. Wiring for cut-outs or a distribution panel 16. Wiring a complete installation. HOUSE WIRING (Knob-and-tube loop system) .Wiring for a ceiling fixture 2 QQO'Ilefl for a bracket Wiring Wiring . Wiring . Wiring . Wiring .‘Wiring 8. Wiring for a single pole flush switch for a convenience outlet for gang switches for control at three or more points for a double pole switch a complete installation XIII-c jXIVF—c. XVI—c XVII~c. XVIII-c. HOUSE WIRING (Armored cable, or BX.) thfithCflNH Stripping armored cable Wiring for a ceiling fixture Wiring for a bracket Wiring for a single pole flush switch Wiring for a gang of switches Wiring for a set of three-way switches Making a complete installation CONDUIT WIRING HtOCDQCDCfifi-CNNH O. Attaching conduit to boxes Cutting and threading conduit Measuring and bending conduit Running in a conduit service entrance Providing cut-outs at the service switch Running in conduit for a ceiling fixture Running in conduit for wall fixtures Running in conduit for a flush switch Running in conduit for a receptacle . Making a complete installation in conduit. ASSEMBLING FIXTURES 1. 2. 5. 4. Pendants with key or pull-chain sockets Wall brackets Electroliers, or drop fixtures Ceiling fixtures INSTALLING FIXTURES AND DEVICES KOCDQO‘JUHbCfiNH rahJH NPJCM . - 1. 2. 3. 4. Pendants Wall brackets Wall, baseboard and floor receptacles Ceiling lamps Bowl fixtures Porch lights Basement receptacles Snap switches Flush switches Three-way switches Three-way and four-way switches . Ceiling switches METAL AND WOODEN MOULDING INSTALLATIONS Providing outlets Running in various lines Crossing lines Making branch taps MAKING AND INSTALLING ELECTRIC SIGNS L. 2. Non-flashing signs Flashing signs XIX" C - XX-rco XDKI-c. XXII-c. XXIII-c. XXIV- C . MOTORS 23 1. Installing and connecting D.C. machines 2. Installing and connecting A.C. RHEOSTATS AND STARTING BOXES 1. Installing and connecting SWITCHES AND A. C. STARTERS 1. Installing and connecting GENERATORS AND SWITCHBOARDS 1. Installing and connecting TRANSFORMERS 1. Installing and connecting 2. Constructing METERS (installing and connecting) l. Switchboard meters 2. Meters in houses, factories, machines etc. MAINTENANCE, TROUBLE-SHOOTING g REPAIR BLOCKSL pg SIEPS I-m. II-m. III-m. IV-m. ‘I-mo VI-m. VII-m. VIII-m. ”IX-m. DRY CELLS l. Prolonging life of dry cells 2. Cleaning and repairing terminals Of dry cells STORAGE BATTERIES 1. Testing a storage battery 2. Charging storage batteries 3. Detecting and removing storage battery troubles BELL CIRCUITS 1. Cleaning and improving connections 2. Connecting on new cells 3. Repairing push-buttons 4. Detecting and removing short circuits 5. Detecting and removing a break 6. Detecting and remedying poor joints 7. Repairing a bell ANNUNCIATORS 1. (Same as under bell circuits) BURGLAR ALARMS 1. (Same as under bell circuits) PUSH-BUTTONS 1. Cleaning and improving connections 2. Repairing defective parts. DUMB WAI TER S 1. (Same as under bell circuits) OTHER MAGNETIC DEVICES l. Detect and remedy troubles 2. Detect, remedy or rewind defective electro-magnets 3. Test for, detect and remedy open circuits, etc. BATTERY LIGHTING Replacing burnt-out lamps Repairing defective lighting circuits Repairing battery switches Cleaning dirty terminals varying the dimming of head lights O‘HPUNH STARTING SYSTEMS IN AUTOMOBILES l. Detecting and remedying poor connections 25 2. Repairing starting switches 3 Detecting and remedying motor troubles 4. Detecting and remedying generator troubles N XI-m. IGIITION SYSTEMS XII-m. XIV-m. XVI-m. XVII-m. XVIII-m. XIX-m. XX-nL l Detecting and remedying troubles in coils 2 Distributor and timing troubles 3 Spark-plug troubles and remedies 4 Detecting and remedying troubles in wiring HEATERS AND HEATER CIRCUITS l. Detecting and remedying troubles SHORT CIRCUITS l. Detecting and remedying 2. GROUNDS 1. Testing for grounds 2. Elindnating grounds 3 Protecting against grounds MOTOR CIRCUITS 1. Testing for shorts 2. Testing for grounds 3. Reversing the direction Of rotation 4. Rewinding SWITCHES l. Repairing loose connections 2. Cleaning conducting parts 3. Other repairs MOTORS (Direct current) Troubles in motors (general) Testing for faults in armatures Repairing armatures Rewinding armatures Repairing field coils Rewinding field coils Connecting up coils and brushes «JOIUHSCJJNH MOTORS (Alternating current) 1. Single phase 2. Three phase A.C. STARTERS l. Deteéting and remedying defects mm. GENERATORS Troubles in generators (general) Testing armatures Repairing armatures Repairing field coils . Rewinding field Coils . Rewinding armatures Connecting up coils and brushes QO‘JUlvpCflNi-J O XXII-m. SWITCHBOARDS l.’ Troubles and remedies XXIII-m. TRANSFORMERS 1. Troubles and remedies 27 III METHODS OE TEACHIEQ ELECTRICAL WORK Methods 2; Teaching Household Mechanics. Since in most cases where instruction of a household mechanics nature is given, the time is very limited and there are a large number of processes to be taught in this short period of time; it is necessary to use devices which will conserve time but which will not detract from the value of the pupils' experiences. When attempting to teach this kind of work to classes of twenty or thirty pupils, the teacher is confronted with quite a problem of organization of material. If all pupils are given a “demonstration“ and then each one given the piece of work to do, it is evident that a very large amount of equipment will be re- quired and that after each lesson the equipment used in giving the lesson will be idle for some time. The job becomes one of teaching several things at the same time and making use of all of the equipment all of the time if possible. Since the work is such that it is not absolutely necessary to follow the course in any Jefinite order, it is pos- sible to have the pupils work on any job for which the material is available and in that way accomplish the desired results. Instruction; 3; Job, Sheets. Individual instruction, or the giving of several kinds of work at the same time requires some means of imparting information and directions to the individual pupils at the time any particular job is being done. This has been accomplished by working out individual lesson, or job, sheets for use by the pupil. The teacher may then use his time in giving 28 individual instruction where it is most needed and the pupils will not be held up in their work waiting for needed instructions. Sample sheets which have been used successfully in several hundred schools are shown herewith as Exhibit No. 1. These may be modi- fied as individual conditions and requirements warrant. It will be seen that each lesson is divided into two more or less distinct parts; (1) the part which tells the student what should be accomplished, and where he may find applications; and (2) definite instructions telling him how he may carry on some activity which will help him in gaining the knowledge desired. Before a job is started the student is expected to study care- fully the first part of the lesson and make sure that he knows what he is trying to accomplish. Then he should proceed with the work, following carefully the directions given. He should remem- ber that he is not doing the work simply to "get something done" but to learn something which will be of value to him in the future. 'Since the pupil who is doing work of this kind is often ,young and must have an interest created before he enters upon the work with the proper spirit, it is often well to include on the sheet something that will point out quite definitely why he should do what he is being called upon to do. This has been attempted on the lesson sheets. The questions to be answered have been placed at the begin- ning of the sheet to stimulate thought on the part of the pupil While at work. This type of sheet is suitable for use by young pupils and 3h1 several different types of classes but the form may be modi- ffiiid for other types of work as will be noted in discussions on job sheets for use in other types of classes. Reference Material; It is evident that where the individual in- struction sheet method of instruction is employed it is imposSible to put onto one sheet all of the reference material required. This necessitates the use of text or reference books or some other suitable reference. Pamphlets or cards may be used to advantage in this respect for some purposes. The text or reference book has the advantage of containing considerable material of interest to the pupil and he may be influenced to read the whole book and perhaps other written material along the same line. A book planned especially for elementary work of this kind known as "Practical Electricity for Beginners" contains the in- formation required for teaching elementary applications. The chapter headings are as follows: Chapter 1. Electricity and Electrical Currents. Chapter II. Electric Conductors and Insulators. Chapter III. Electrical Pressures. Chapter IV. The Flow of Electrical Current; Electrical Circuits. Chapter V. Battery-Lighting Circuits. Chapter VI. Heating Effects of Electrical Current:; Practical Applications Chapter VII. Fuses and Their Purpose. Chapter VIII. Heater-circuit Troubles; How to Detect and Remedy. _ Chapter IX. Incandescent Lamps and Their Use. Chapter X. The Operation of Electric Lamps. Chapter XI. Electrical Measurements. Chapter XII. Dangers Involved in Using Electricity; How to Avoid them. This book has been used successfully in a great many classes where elementary, practical work is given. Reference material may be provided also on cards such as shown as Exhibit No. 2. On these cards, actual materials may be mounted. The cards may be hung on the wall or kept on file in a cabinet and used by the pupils as needed. Methods pf HandlinggEquipment. Since there are numerous pieces of equipment required for giving work of the household mechanics type, and the possibility of loss and breakage is very great, and since in many cases the period of time is very limited, it is necessary to provide some method of distributing material quickly, to relieve the pupil of unnecessary work, and to keep the material required for each individual lesson intact. Also it is often desirable to furnish the pupil with something that is the equivalent of an actual installation in the home. Such things might be flush switch installations, snap switch instal- lations, drOp cord installations, and the like. In order to meet these and other requirements, a series of panels, or boards, have been provided upon which the required materials have been mounted for use by the pupils. These panels have been made removable shelves of suitable cabinets and have been numbered to correspond with the number of the lesson for which they are intended. The cabinets have been made of sheet metal and the panels of panel stock about one foot square. A large number of these cabinets of equipment have been used with success. An illustration of the original cabinet of wood and some of the equipment boards partially completed is shown as EXhibit No. 3. neoeic suavemun 3'. :.-LJ salt .fu H invfi («j eoixtsxiaem altnssuc-a ...' 'to .. 1. w '- z ' no. x Lawn.“- ,Jsetp mxsv agnixe'm "t.“ ssn’ :; ,sifit‘macQ .hsxtmif Vtev ai 0'}. 1« “Hi... “33 .:s.3 VIE -‘ izlweism sniiudiuieit in :C.Jei enca “LEVCZQ o: t 4901 o3 bus .XTO‘l '_'T;“£.;'i:>1:'3431‘3£ .(U J:IL.!IJ" .‘JiiJ BVQII 061A .Joadni morsni +susiliini dons eel LETIUpe Jud: Batman-toe .U.,..-‘_‘ as. .f anvil} o: siren-P .fiflxa .smcd , - . - g , 0’ ' ' 3 . "..J a; :1C-‘..H.' J..- .. "'11-. 43.1304? In: .C- We «Emmi {(511918 ({J—lflfl, .aflotanibweni 110.! iwe new“: .sfiif 9d: bun .asoirsfinseri axe; serum i; ,.-‘..?::9r:~)'<§..;,v,:1"3.9.1.30 has mam Js‘o v.1 ': siensq-eesnT ,.b511upex and norms aoqg bsbiv01q need ave; .351 cc .a'iqha 3d! Id was 103 beanuom weed svsd ban eJeatdso sidhdtue To ssvfsna sfdflvomax sol honest as: to zedmrn an: Aniw bfloqssxtou «3 Seeds Igfqhfim head svsd LJflnIdut 9d: .bsbassni ..S¢&§p§fJoOT ano Jscup aeoJo Isnsq lo eienxq - ."‘ q .- _ '* a a 531w.b5§895§9d even insmqruye is assnxusc 559:: it banghpGW*lo':enidso innigiso ndi lo noiJs-Jcslli 'fljifiwoda ai betsiqmmb_g[iei:1cq 521306 Shamfiw «f7 31. In some cases equipment may be kept in individual boxes and the boxes checked out and returned after the work has been com- pleted. The panels upon which flush switch, snap switch, and similar installations are provided are connected to cleat receptacles on the front and the back of the panel so current can be fed thru an extension pend with a plug on both ends and a lamp may be screwed into the receptacle on the front of the board and con- trolled by the switch. Methods 2: Teaching Elementary Construction Work. Elementary construction work may be given in a manner similar to that in which manual training is given but a few additional materials and tools are required. The extent to which work of this nature can be carried on will depend upon the time devoted to the work and the materials and tools available. However, there are a great many things which can be constructed with a very limited number of materials and tools. A few simple motors, heating devices and transformers can be constructed very readily with but a few sizes of magnet wire, and sheet metal. There are a great many descriptions of devices to be found in such magazines as Popular Science and Science and Invention but it will often be found difficult to make these devices because of a lack of numerous materials and tools. One who is attempting to give instruction for the first time: c.n4ron#cd ~1+h along construction lines is up against the prOposition of furnishing information on methods of construction. It is Possible to give a dmponstration and then have every pupil make 32. the device constructed but in many cases this is not desirable because large numbers of tools are required. If several differ- ent Jobs are given at the same time, all of the equipment can be kept in use. In giving construction work it is essential that the pupil be influenced to put his best efforts into the work and to make the finished product as neat in appearance as possible with the available materials and tools. However, it is possible that pupils will be able to make some simple devices which are not what could be called beautiful but which furnish some very good work and during the construction of which the pupil learns many things about electricity and magnetism. This is true to a cer- tain extent of the simple experimental motor described on the sheet shown as Exhibit No. 4. Never-the-less hundreds of boys, and even men, have constructed this motor out of a bolt and some pieces of tin and in every case the motor has run and afforded its builder considerable satisfaction. During the brief period of time required for making the motor, the builder has learned several important things about electricity, magnetism and motors. After the motor has been completed and found to run satis- factorily, it is possible to make a reversing switch for chang- ing the direction of rotation and a rheostat for controlling the speed. The pupil has an opportunity to develop his original- ity and inventive ability in making these things. While constructing simple devices it is well to have avail- able for use by the pupil a text or reference book which gives in detail processes and uses of materials, or perhaps instructions in the form of sheets such as shown in Exhibit No. 5. Sheets of 33 this kind are a great help to both the pupil and the teacher. Making Eggpsformggg; Of the devices suitable for construction in the school shop, the transformer is perhaps the best. All that is required for making a transformer is magnet wire and sheet iron for the core. The magnet wire is usually readily available from electrical stores and the iron for the core can be obtained readily from almost any sheet metal worker. When having pupils construct a device of this kind, it is well to furnish complete details and to have these details carried out carefully. It is well to suggest methods of Operation and then permit the pupils to do the work in the most convenient manner provided it is done satisfactorily. Instruction sheets for use by the pupils when constructing devices of this kind may be somewhat as those shown as Exhibit No. 5} In connection with elementary construction work it is often well to give some wiring and connecting up of devices. The chief aim is to give pupils mental pictures of circuits and to teach accuracy and careful workmanship. For use in presenting this kind of work, instruction sheets such as those in Exhibit No.2, for battery lighting problems may be found satisfactory. Methods 2; Teaching 'Finding" 3933;, The chief aim.in giving finding work being to give practical experience, it is evident that the problem.becomes one of presenting as much vocational material as possible within a limited period of time. It is intended that the pupil be givenjas clearly as possible,ideas of the various kinds of vocational work. The content of the course may be selected from the content of a similar vocational course but the circumstances under 34 which the work is given may be considerably different . In taking a vocational course, the pupils or men have decided that they want to learn a particular trade or vocation and they are compar- atively old. The type of pupil who is given finding, or tryout, work is comparatively young and he does not know what he wants to do or what he is able to do. Rotatinnghru Shops. If there are several shops in which the vocational work is given and it is possible to work in small groups of finding pupils for short periods of time in each shOp, this is a satisfactory method of giving the young pupils an idea of the various kinds of work. They do some and see others at work also. However, in many cases all of the finding work must be given in a single shop entirely separate from vocational shops. Finding Work In 3 Single Shqp. If the finding work in a single shOp must be given to large numbers of students in short periods of time it is necessary to use special methods. In giving this type of work in "House Wiring", it is pos- sible to have one wiring frame on which several boys may work at the same time. One boy may install the wiring for a ceiling lamp to be controlled by a snap switch, another may be wiring for a bracket, still another may be wiring for a flush receptacle, and other pupils may be doing other Jobs at the same time. After the wiring has been completed, other members of the class may install the switches, fixtures, etc. and the whole group may then inspect the finished job and see it in operation. In this manner a large number of pupils may be given quite a def- inite idea of house wiring in a very short period of time. Instruction sheets such as shown in Exhibit NO. 7 may be used to advantage in giving this work. 35 Likewise in motor work each boy may be called upon to wind a few coils for a motor, then tape a few, and then put a few into the slots. Then after the work has been completed every pupil who has worked on the motor may see the complete job and in that way get quite a definite idea of the work. In a similar manner one automobile ohasis may be used by a large number of pupils for learning what automotive electrical work is like. One boy may be cleaning the terminals of a storage battery, another changing spark plugs, another changing the points on a Ford coil, etc. etc. and all may have an opportunity to see what the others have done and gain quite a broad knowledge of the work involved even tho the actual time spent on the job by each individual is very limited. Reference Material. One ofhhe big jobs in connection with giving finding work in the manner described, as in the cases where other types of individual instruction is given, is that of organizing material and providing suitable references. If possible, it is well to refer pupils to small books covering quite completely but in a simple and easily understood manner the work involved in the particular vocation which he is studying. If these books are sufficiently interesting as well as to the point, the pupils will in many cases make careful studies of the work both in school and out of school and in that way gain much knowledge of many different lines of work even tho they are given very little work in school. An attempt has been made to meet these demands in two cases ‘HY small books entitled "Fundamentals of House Wiring" and [Automotive Electricity- Simplified.". 56. Fundamentals of House wiring is a 67 page book covering briefly the things involved in house wiring. The chapter head- ings are as follows: Chapter I. Important Points to Consider Chapter 11. Suggestions for Safe Installations. Chapter III. Service Arrangements and Cabinets. Chapter IV. wiring new buildings (Knob-and-tube) Chapter V. Conduit and Armored Cable Work. Chapter vI. installations In Finished buildings. \ Automotive Electricity-Simplified is a 128 page book cover- ing briefly the things involved in automotive work. The chapter headings are as follows: Chapter 1. Fundamental Principles Chapter II. Electrical Pressures; Storage Batteries Chapter III. Storage battery Work Chapter Iv. Electrical Applications In Automobiles Chapter v. Electrical Circuits Chapter VI. Eagnets, Magnetism, and Motors Chapter VII.. Iagnetos, Generators,and Coils. Chapter VIII. Electrical Troubles and Remedies. In some cases it is possible to make use of strictly voca- tional material but often this is not suitable for use by young pupils and it may not create interest. Methods 2: Teaching Vocational Work. Methods used in teaching vocational work should be as nearly as possible those used in Commercial practice on productive work. It is evident, however, ‘Uaat the man in charge of an educational inatitution in which large numbers of beginners as well as some advanced students are being taught trades is in a somewhat different position than is the foreman in a shop where most of the men are experienced and there are but few beginners. Then, too, the commercial shop is on a production basis and is continually supplied with new work. The school shop instructor has very few what could be called experienced workers,practically all of the pupils being of the apprentice type. It is impossible in many cases also to do all productive work that is of a suitable type. In the school Shep it is often necessary to use improvised methods for giving certain training. In house wiring it is impossible to give practical work all of the time without suitable frames and it is impossible to do work that will be permanent in its entirety. This necessitates the removal of much of the wiring after it has been completed and tested out, but results obtained by this method have been very satisfactory and the student who completes the work in the school shOp finds it very easy to enter the employ of electrical contractors and make' good. It is often true also that motors rewound by one class must be stripped and rewound by others instead of being put into use, but in many cases the wire can be used for other purposes and where the w0rk is not commercial the student can be given sufficient tine to learn fully every step in the various process- es. In giving elementary armature winding where it is desired to handle several pupils in a group, it is possible to make use of model wooden armatures which may be actually wound and tested. In the case of simple two-pole windings, permanent magnets may be used for the field. 38 Teaching House Wiring, House wiring has been taught successfully in a school shOp by means of booths or frames. Each student is given a number of jobs to do. The student is furnished with a wiring plan or works out one in the drafting room and proceeds to install all of the possible arrangements. For use in teaching this work, a trade text entitled “House Wiring" has been deveIOped. This book is written on a job basis. That is, each job to be done is carefully analyzed and then the details of instruction are given. A typical des- cription follows: Job No. l. References;- Jobs 45 and 46; Chapter VI. Operations Necessary £2_Perform the JobL .. Locate the outlet Select and cut the cleat. Install the cleat. ‘ Install the outlet box, if one is used, and bore holes for the entrance of the loom-covered wires. . Make the necessary runs of wire. 6. Test the installation and call for an inspection. ()1 scum—a Materials Required. Wooden cleat at least 7/8" thick, 6" wide and sufficiently long to reach from one joist to the next; No. 14 R.C. wire; porcelain knobs (split); porcelain tubes; non-metallic flexible tubing, or loom; outlet box if required; a few nails (6 or 8 penny) for nailing cleats to joists; soldering materials; rubber tape or splicing compound; and friction tape. Tools Required. Saw; pliers; hammer; knife; brace and bit (ll/16); rule; test set; soldering kit. Qgscriptiqp 92 Operations; (Under this head, complete descriptions with illustrations are given including the symbol used for representing a ceiling outlet, a typical ceiling fixture, details of how to locate the center of a room, installing the cleat, the circuits involved, the Underwriters' rules, how to run wires, etc.) (At the end of each job description is given a series of questions which are intended to test the pupil. These are as fOIlows:) anestions. 59 How is a ceiling outlet represented on plans? When is the "roughing in" work done in a building under construction? What does the work comprise? Why is a wooden cleat necessary? How can the position of the cleat be located? What should be the thickness of the cleat? About what should be the width of the cleat? What must be placed on the wires from the last knobs thru the cleat? How far should it extend thru the cleat? Why is it necessary to have 6" of wire extending down into the room? What are the Underwriters' rules relative to an installa- tion of this kind? {\JH KO (DQCEO‘Hh-Cfl f" O This book, "House Wiring" is divided into six chapters as follows: I Chapter I. Knob-and-tube Wiring. Bap System. 16 jobs Chapter II. Knob-and-tube Wiring. L00p System. 9 jobs Chapter III. Armored Cable or BX Wiring. 8 jobs Chapter IV. Wiring in Conduit. 11 jobs Chapter V. Miscellaneous Construction Jobs. 6 jobs Chapter VI. Things a Wireman Should Know. 25 topics including trade terms. The complete work comprises 50 jobs and 219 pages of text material with 209 illustrations. After this course has been completed, the student has had sufficient experience to prepare hinlto go to work with a contractor. Teaching_Motor Work. In the author's shOps the students are 4O given actual rewinding work on the various types of motors, each student completely rewinding at least one of each of the various kinds of direct-current, single-phase, and poly-phase motors . Some of this is commercial work brought in and other is that provided by permanent equipment in the shep. To successfully teach.motor work requires large numbers of teaching aids such as instruction sheets and reference material. Samples of such material which have been used successfully are included herewith as Exhibit No. 8. More and more of this kind of material is being developed from day to day and it is hoped that in the near future this too will be put in the form of a book which is probably the most convenient form for use by students, teachers and those engaged in commercial work. EXHIBIT HO. L Samples of lesson sheets for use by young pupils in the study of practical elementary electricity. ELEMENTARY ELECTRICITY 3-11 Edited by B G r P ll' h d EORGE A. WILLOUGHBY “3 15 e by K. G. SMITH y _ THE MANUAL ARTS PRESS, PEORIA, ILL. LESSON SHEETS Student’s Name : ................................ Class : ......................................... Name of School: ................. . .............. Date Begun: ................................... DISMANTLING, REPAIRING, AND ASSEMBLING A HEATER EXTENSION CORD What You Should Gain from This Lesson.— , The ability to assemble a new arrangement, or to replace parts of a heater extension cord arrangement. Also the ability to select the right kind of materials and to guard against possible troubles. Questions to Be Answered.— I. What is a heater cord arrangement used for? 2. Of what does it consist? 3. Explain in detail how to remove a two-piece receptacle plug from a heater cord. 4. Explain how a separable plug is attached to a cord. 5. Why must great care be exercised when making the connections to the plug terminals? 6. What may happen if the bare wires touch each other? 7. What is the purpose of the knot inside the plug? 8. Explain in detail how a heater attach- ment plug is removed from the cord. 9. Give, step by step, the manner in which an attachment plug is connected to a cord. IO. What may cause trouble in a heater cord? II. What trouble may exist in the receptacle plug? 12. What in the heater attachment may cause trouble? References.— Willoughby, Practical Electricity for Beginners. Chap. VIII; Chap. XII, Sec. 99, 102, and 103. Willoughby, Electrical Conveniences in the Home. Chap. IX; Secs. 89 and 90. Applications of Knowledge Gained.— All portable heaters are supplied with electricity thru an extension-cord arrangement of some kind. Even tho great care be exercised when using these, there is a possibility that continued use will cause wearing of the cord, loosening of the connections, or something else which will eventually cause trouble. It is obvious that a knowledge of the repair of the arrangement when any such troubles arise is a valuable asset to anyone. Then, too, it is often desirable to make up new arrangements or to replace plugs with others which are more suited to given requirements and which are perhaps more convenient. There are a great many possible applications of the knowledge gained by doing this work. B-ll Materials Required.— Board No. II, or A complete heater-cord arrangement, including a separable plug, a cord, and an attach- ment plug. Operations.— 1. Remove the receptacle plug from the cord. 2. Re-connect the plug to the cord in the proper manner. 3. Remove the attachment plug from the cord. 4. Re-connect the attachment plug to the cord in the proper manner. Description of Operations.— To disconnect a separable plug from a cord is not a difficult task. The order of operations are as follows: (1) separate the parts of the plug, (2) loosen the screws securing the wires to the terminals, (3) untie the knot in the cord, and (4) remove the plug. ‘When connecting the plug to the cord', the operations should be performed in the following manner: (I) push the cord thru the open- ing in the plug, ' (2) clean the wires and twist each so that none of the strands project, (3) tie the knot in the cord, (4) loosen the screws and wrap the wires carefully once around them being sure that the wires are thoroly insulated from each. other, and (5) tighten the screws firmly. To remove the attachment plug: (1) remove the small bolts and _ separate the parts of the plug, (2) loosen the screws in the terminals, Parts of a Separable Plug (3) remove the terminals, ('4) remove the coiled wire from the cord. To attach the plug: (1) Slip the wire coil onto the cord, (2) separate the wires to provide for attaching the metallic sleeves, (3) connect the wires to the sleeve terminals, making sure that bared portions of the wires do not touch each other and that the strands of the individual wires are twisted together, (4) put the sleeves and wires into place in one half of .the plug, (5) put the wire coil into place, (6) place the other half of the plug over the wires and sleeves and put the small bolts into place. Be sure to see that the parts fit' together properly before the nuts are tightened on the bolts or the plug may be broken. Bare spots on wires may be covered with friction tape, but it is best to replace the cord if it is badly worn. Testing Your Ability and Knowledge.— After you have assembled the cord, compare your work with a new commercial product or with others which have been tested out and found satisfactory. Try your cord out on any available heating appliance. See if you can answer all of the questions. Does the knot inside the receptacle plug relieve the terminal of any strain? Are the strands of wire all well secured under the screw heads? Does the receptacle plug fit together properly? Does the attachment plug fit together properly? Was it injured in any way? Date Completed .......................... Instructor's Grade ................... . . . . . El: 1 an and- )i operates the wire I: 9 parable l4? 5 to prmffic 11g aural-3 .idual “lit lg. (El PC: res and l: he nuts 1'5 prl‘ldllfl C" rr-y ELEMENTARY ELECTRICITY 3-12 Edited by Published by K. G. SMITH By GEORGE A' WILLOUGHBY THE MANUAL ARTS PRESS, PEORIA, ILL. LESSON SHEETS Student’s Name: ................................ Class : ......................................... Name of School: ..... . .......................... Date Begun: ................................... DISMANTLING, REPAIRING, AND ASSEMBLING A LAMP EXTENSION CORD What You Should Gain from This Lesson.— The ability to assemble a new lamp extension cord arrangement, or to replace parts of such an arrangement. Also the ability to select materials for such an arrangement and to guard against possible troubles. ‘ Questions to Be Answered.— 1. What are lamp extension cords used for? 2. Why should one be able to connect a plug onto such a cord? 3. How is a swivel plug removed from a cord? 4. How is a socket taken apart. 5. How is it attached to the cord? 6. What kind of sockets should be used in damp places or in places in close contact with the ground? 7. What troubles may exist in an exten- sion-cord arrangements? 8. State, in their order, the steps required to connect a plug to an ex- tension cord. 9. State, in their order, the steps required to connect a socket to a cord. References.— Willoughby, Practical Electricity for Beginners. Chap. X, Sec. 76, 81, and 84; Chap. VIII, Sec. 57 and 60; Chap. IX; Figs. 40, 43, 44, 45, 46, 48, 51; Chap. XII, Sec. 99, 100 and 102. Willoughby, Electrical Conveniences in the Home. Chap. IX; Sec. 89. Applications of Knowledge Gained.— There are so many cases where the ability to make up or repair lighting extension cords can be applied that it is unnecessary to cite definite examples. Nearly everyone is familiar with this. It is very important, however, that it be known that brass sockets on extension cords are dangerous in some cases if they are not con- nected very carefully, which makes it more important that one be familiar with the making up of these arrangements. During one year two people were electrocuted in one community according to newspaper reports. One, a boy in Flint, Michigan, when he took hold of a furnace door as he held a brass socket in his hand; and the other, a man in Bay City, Michigan, when he picked up a brass socket while at work in his garage. When extension cords are to be used in such places, porcelain sockets should be used, however, these accidents might not have happened had the wiring been exceptionally This Could Have Been good. Avoided , , ,___._i _ ,_.l‘fi Materials Required.— . ‘ B-12 Board No. 12, or A complete lamp extension cord arrangement including a non- separable, or swivel plug, a brass socket, and a bushing. . Operations.— I. Disconnect the plug from the extension cord. 2. Connect the plug to the cord. 3. Remove the socket from the cord. 4. Connect the socket to the cord. Brass Shell and cap for cxtensron cord. Description of Operations.— These descriptions refer especially to an arrangement consisting of a non-separable plug, a brass socket, and a lamp cord. This plug consists of three parts which may be separated by turning. (See Fig. 40, Prac- tical' Electricity for Beginners.) The outside shell which makes the connection thru the threads to the inner part of the receptacle, is so arranged as to be revolvable about the rest of the plug without twisting the cord. This is held in place by a non—conducting piece which screws into the part of the plug to which the connections are made. One wire of the cord is connected to a screw on the tip of the plug and the other to a screw on the side of the plug which forms a connection, thru a metallic piece, to the removable shell when it is in place. To remove the plug from the cord: (1) turn the non-conducting piece counterclockwise until it can be pushed up onto the cord, (2) push the metallic shell back onto the cord, ( 3) loosen the screws which hold “the wires in place, and (4) remove the three parts from the wire. To connect the plug to the cord: (1) slip the non-conducting part of the plug onto the cord, (2) slip the shell part onto the cord, ( 3) see that the wires are properly separated and prepared for making the connections, (4) pass one of the wires up thru the plug and make one complete turn around the attaching screw, ( 5) tighten this screw down firmly and see that no wire extends beyond it, (6) pull the second wire up thru the side of the plug and attach it properly, removing any excess wire, (7) push the shell piece up over the attached part, and (8) screw the non- conducting piece into place. To remove the socket: (I) apply pressure with the thumb at the point marked “press’ and separate the parts, (2) slip one part of the shell onto the cord and remove the other, (3) loosen the terminal screws and remove the wires, (4) untie the knot and pull the cup-shaped part of the shell off of the cord, and (5) loosen the set screw and remove the insulating bush- ing from this part. To connect the socket to the cord: (1) place the insulating bushing in the cup-shaped part of the shell and place both on the cord, (2) prepare the wires for making the connections, ( 3) tie the knot in the wires, (4) make the connections to the terminals, making one complete turn, and remove any excess wire, ( 5) tighten the screws firmly, (6) place the insulated brass shell over the arrangement and push the cup-shaped piece into place over it. ’ Testing Your Ability and Knowledge.— Test the extension cord after you have completed assembling it and compare your work- manship with that on a commercial product, or one of the same quality. See if you can answer all of the questions. Date Completed .......................... Instructor's Grade ........................ . ELEMENTARY ELECTRICITY 3-13 Edited by By GEORGE A. WILLOUGHBY PubliShed by K. G. SMITH THE MANUAL ARTS PRESS, . PEORIA, ILL. LESSON SHEETS Student’s Name: ................................ Class: ......................................... Name of School: ............................... Date Begun: ................................... TESTING AND REPLACING FUSES What You Should Gain from This Lesson.— The ability to understand the purpose of fuses, to test for “blown” fuses and to replace them without danger. Questions to Be Answered..— 1. What are fuses for? 2. Describe a plug fuse. 3. What might happen if a fuse were omitted from a circuit? 4. Why is it dangerous to put a cent or a piece of wire under a fuse? 5. What must be borne in mind when replacing fuses? 6. What might cause a fuse to “blow”? 7. How do you detect a blown fuse? 8. Describe in detail how to test fuses. 9. If a fuse blows as soon as it is screwed into the receptacle, what is the trouble? 10. What should be done if a fuse must be replaced at night? References.— Willoughby, Practical Electricity for Beginners. Chap. VII; Chap. VIII, Sec. 59 and 61; Chap. X, Sec. 76 and 84; Chap. XI, Sec. 91 and 92; Chap. XII, Sec. 99, 102, and 103. Application of Knowledge Gained.— Mrs. Duff had just finished her breakfast dishes and got her ironing board ready so she could hurry thru her week’s ironing. She had ironed only one shirt when something happened—there was a flash and the iron cooled off. Try as she would, she couldn’t get it to heat up again so she finally gaVe up in disgust, put her ironing away and waited for her husband to come home to see if he could fix the iron for her. As evening approached, she pushed a switch button to turn on the lights but the lamps refused to operate also. When her husband came home she explained what had happened and he replied, “Why, you simply blew a fuse. There must be a short circuit in your iron cord.” He went into the basement, located the blown fuse and replaced it with a good one. Then he turned on the lights and inspected the fiatiron cord, and found that the insulating covering on the wires had been worn and the bare wires touched each other. He wound some friction tape around the bare spots on the wires so Mrs. Duff could do her ironing and a few days later bought a new piece of cord and removed the plugs from the old one and connected them to the new one. Mrs. Duff hasn’t had any trouble with her iron since that time. To replace a fuse, it is necessary to determine which fuse has been blown and to select a good one for use in its stead. Sometimes several fuses are available, some good and some blown. Then it becomes necessary to test them to separate the good ones from the blown ones. The following tests will teach you how to do this. B-13 ' Materials Required.— Board No. 13, or An installation including a cut-out, and several fuses. Arrangement of Materials Operations.— 1. Locate a blown fuse. 2. Select a good one for its place. Description of Operations.— First of all, remember that care must be exercised when removing or inserting fuses. See that the fuses are “dead" if it is possible to disconnect them by opening the circuit leading to them. The fuse blocks in a home may be found near the entrance or in a special cabinet but for practice any circuit containing a cut-out, or fuse block, may be used. The block may be attached to a board and supplied with current from a receptacle or socket by the use of a cord with a plug on both ends. Another receptacle may serve as the circuit leading from the block. In any case the current should be led into the metallic pieces in the center of the bottoms of the fuse receptacles. _ Then, if it is necessary to replace fuses without opening the circuit, the metallic shells of the fuses will be “dead” as soon as they are turned out a little way. Loosen the screws in the center of the bottom of one of the fuse receptacles and be sure that the current is led into the bottom. If the current is led into the block thru an extension cord with a plug on both ends, don’t remove the plug at the block while making tests. Pull the plug from the scroll receptacle or dis- connect the circuit. I After having made suitable provision for furnishing current to the fuse block, or in a real installation, proceed as follows: With the main switch open, or the wall plug removed, place a lamp in one of the fuse receptacles and a fuse in the other, and another lamp in the circuit. Then turn on the current. If both lamps light dimly, the fuse in the block is good. In this manner, any number of fuses may be tested. Remember, however, to open the circuit, pull the wall plug or open the main switch, every time you remove or insert a fuse. Test all of the available fuses and finally insert two good ones and test to see if the lamp in the circuit lights properly. Testing Your Ability and Knowledge.— Your ability to do this correctly is determined by the results you get and the accuracy with which you can select good fuses without endangering yourself. See if you can answer all of the questions to check your knowledge of fuses. Out of a large number of fuses how many good ones did you find? How many blown ones? Date Completed .......................... I nstrnctor's Grade ........................ fuses. 3:: t leading It met but II? ' be attaciti cord with; f lllli‘t‘h'. :1 ; of the its: the meal: be sure that Clldi. (it'll: [dill 0T “‘5 ,f the use the Cumin ritch. 6W? the lamb :urflcl’ “1h liim’ bjcxl‘: ”k ’/‘ ELEMENTARY ELECTRICITY 3-14 ' KECC’iieSiME'IH By GEORFE A’ WILLOUGHBY THE Mlettiiiihi’RES’ PRESS, PEORIA, ILL. LESSON SHEETS ‘ Student’s Name: ................................ Class: ......................................... Name Of School: ............................... Date Begun: ................................... TESTING FOR AND REMOVING SHORT CIRCUITS What You Should Gain from This Lesson.— The ability to detect a short circuit and to remove it. Also the ability to guard against forming Short circuits. Questions to Be Answered.— - I. What is meant by a “short circuit”? 2. What is an overload? 3. How can a short cir- cuit be located? 4. What are some of the common causes of short circuits? 5. How would it be possible to use lamps in some parts of a house even tho a short circuit existed in one circuit? 6. Why is it necessary to turn on only one lamp at a time when testing for a short circuit? References.— ~ Willoughby, Practical Electricity for Beginners. Chap. X, Sec. 74, 75, 76, 84, 85, and 86; Chap. VII; Chap. XII; Figs. 51 and 52. Applications of Knowledge Gained.— In the everyday use of electrical equipment, especially in the home, various things such as the wearing off the insulating covering Of wires, or the connecting of defective extension cords may form; short paths for the electricity, or short circuits as they are called. Such a con- dition usually causes the blowing of a fuse, and until the trouble is located and removed, new fuses will blow as fast as the blown ones are replaced. For example, suddenly the lamps on some circuit, or perhaps all of those in the house, may go out while attachments are being used and the cause may not be detected by those making use of the attachments. This may be due to overloading the fuses by having too many things Operating at one time which causes the drawing of too many amperes, (see Chapter XI, Sec. 91 and 92 Practical Electricity for Beginners) or it may be due to a short circuit someplace. In such a case, some of the attachments Should be disconnected, so there is no possibility of an overload, and a test made to see if a short circuit exists. If one is detected, it must be located and removed before a new fuse is put into place. Something went wrong with all of the lights in Mr. Thompson’s apartment. He thought a fuse had been blown so he bought some new ones but as fast as he put them into the fuse block they blew also. . It happened that Mr. Thompson had connected up a table lamp which he had made, but he hadn’t tried it out and had not thought that it might not have been wired properly. After having gone one night without lights he called an electrician who immediately turned Off all of the lamps. Then he placed a lamp in the fuse block, and one good fuse, and turned on one lamp at a time. When he turned on the table lamp it failed to light, and the one in the fuse block “burned” brightly. He had located the trouble. B-14 Materials Required.— Board NO. 14, or . Two or three circuits leading from a fuse block. Three lamps Of the same wattage. Arrangement Of Materials Operations.— 1. Test for a short circuit. 2. Locate a short. 3. Remove the cause Of the trouble. Description of Operations.— If an actual installation is not available for use, arrangement can be made by using three receptacles, representing three different circuits in a house; a fuse block; and an additional receptacle for furnishing current tO the circuits thru a cord with a plug on both ends. This, Of course, simply takes the place Of an actual installation for instruction purposes only. The prin- ciples involved are the same nevertheless. When electricity is supplied tO equipment thru a cord with a plug on both ends, always use a two-part separable plug on the end where the connection to the source Of current is tO be made and remove this plug whenever anything is tO be done. Don’t remove the plug from the re- ceptacle on the board until the work has been completed. Failure to Observe this may be dangerous. ' Having made prOper provision for doing this work, proceed as follows: 1. Place good fuses in the fuse block and gOOd lamps in the circuits and test them. 2. Disconnect the circuits, or pull the main switch; remove one Of the fuses and put a lamp in its place. 3. W ith all Of the lamps turned out but one, turn on the current and note the brilliancy Of both lamps. _ 4. Turn another lamp on and note the effect. 5. Screw a defective (short circuited) plug or other device into a receptacle and note the effect. (If the lamp were not in the fuse block, a fuse would be blown when this is done.) 6. Remove the defective circuit and note the result. From the results Obtained draw conclusions as tO how you can test any installation for a short circuit. Testing Your Ability and Knowledge.— Your ability tO apply this method to an actual installation where the location of the short circuit is not known will be a test Of your knowledge and skill. See if you can answer all Of the questions. Date Completed .......................... Instructor’s Grade ........................ using thffi 1 allelitiiur; 5, This. '33. The [fit alwayi 1‘5 to he 211:3: am the 73' lis 1m}- :e and put: Illlllfillil' ml Me It. 5 dc 116- i‘ alien 1" ' )f the 513*” ELEMENTARY ELECTRICITY 3-15 KggieSlM’i'i‘iH By GEORGE A' WILLOUGHBY THE MleiilAiihiilRig PRESS, PEORIA, ILL. LESSON SHEETS Student’s Name: ................................ Class: ......................................... Name of School: ............................... Date Begun: ................................... REMOVING, REPAIRING, AND REINSTALLING OR REPLACING A FLUSH SWITCH What You Should Gain from This Lesson.— T he ability to select, use, repair and replace flush switches. Questions to Be Answered.— 1. What is a flush, push-button switch? 2. What is it used for? 3. Describe in your own words a flush switch. 4. Which button is pressed to turn the lights on? 5. What is the advantage Of having the switch Operate with a snap? 6. How is the switch attached to the switch box? 7. How are the connections made to the terminals? 8. What should be done when these con- nections are made? 9. Which of the buttons is placed up? 10. What is a switch plate? II. How is it attached? 12. What may happen in a switch to cause trouble? References.— Willoughby, Practical Electricity for Beginners. Chap. X, Sec. 74, 75, and 76; Chap. XI, Sec. 91 and 92; Figs. 49 and 55. Willoughby, Fundamentals of House Wiring. Chap. IV; Sec. 53; Figs. 19 and 20. Applications of Knowledge Gained.— The switch for controlling the living-room lights in Mrs. Rossman’s home was near the front door, and, as some Of her friends came tO spend the evening, someone slammed the door and out went the‘lights. Those in the hall remained unaffected however. Just what had happened none Of the women knew, but it happened that Mrs. Rossman’s nephew lived in the next house and he had studied practical electricity, SO she sent for him. He knew immediately what had happened and explained it in this way. “There are two wires connected tO the switch and they are held in contact with its parts by small screws. The jar caused by the constant closing Of the door has caused one Of them to become disconnected.” He Simply removed the switch cover with a screwdriver and made the proper connection tO the switch. “Aren’t you afraid of being electrocuted ?” asked one of the women. The boy laughed and said, “There is absolutely nO danger in doing this or any other electrical work if one knows what precautions to take. We were taught these so I am not afraid of getting a shock.” B-15 Materials Required.— Board NO. 15, or An installation including a flush switch. _. Operations.— I. Remove the switch plate. 2. Disconnect the wires. 3. Remove the switch. -4. Install the switch. 5. Make the connections tO the switch. , 6. Attach the plate. Parts Of a Flush SWItch Descriptions.— A flush switch consists, essentially, of a box-shaped porcelain piece in which the movement and the terminals are mounted. The terminals are brought to the front where brass screws are provided for attaching the wires. The switch movement consists Of a piece Of brass or copper arranged with a small Spring and two buttons in such a way that pushing on the buttons causes the connecting or the disconnecting Of the terminals with a snap. The pushing Of the white button causes the switch to close and the pushing Of the black one causes it to Open. The quick closing and Opening, especially the latter, reduces the possibility Of a flash Of electricity, or an arc, tO a minimum. The two push-buttons extend thru a metallic piece in which holes are provided thru which the screws used in attaching the switch to the box are passed, and two others threaded, or tapped, for the screws used in attaching the plate, or cover. When this type Of switch is installed, the wires are brought into the box and out the front. The switch is then placed in the box and attached tO it by screws passing thru the metallic piece on the front Of the switch. The wires are then prOperly prepared by removing sufficient insu- lation and scraping them clean, and attached tO the terminals by placing a loop under the attaching screws and tightening them down firmly. The plate is then attached by two screws which turn into tapped holes on the front Of the switch. It is customary to place the white button at the top. . TO inspect and repair the connections on this type of a switch is easy, the only tOOl required being a screw driver. The plate is readily removed by simply taking out the two screws that hold it in place. When this is Off, the terminals are visible and readily accessible. They may need tightening or cleaning. Be sure to avoid breaking the wires because it is quite likely that it will be impossible to make new loops on them because Of their limited length. Testing Your Ability and Knowledge-é Your ability is tested by the neatness Of the work which you do and the satisfactory Opera- tion Of the switch after you have installed it. See if you can answer all Of the questions. Does the switch operate properly? Is it vertical? Did you scratch or bend the plate? Did you strip any Of the threads? Date Completed ............. .......... . Instructor's Grade........................ emovemer . screws. at: is or can: thins causes f the “hit: The quick "icity, 01a h holes at d. and at: .t the front etallit gist? iiciem insu- under it two SUB“? ‘ the white 1+0] return screws [£1.21 T he]; m3? 1p055lilll5 E 100' 0PT. ELEMENTARY ELECTRICITY 3-16 Edited by Published by K. G. SMITH By GEORGE A' WILLOUGHBY THE MANUAL ARTS PRESS, PEORIA, ILL. LESSON SHEETS Student’s Name: . .' .............................. Class: ......................................... Name of School: ............................... Date Begun: ................................... REMOVING AND REPLACING, OR RE—INSTALLING A FLUSH RECEPTACLE What You Should Gain from This Lesson.— The ability to select, use, repair, or replace flush receptacles. Questions to Be Answered.— I. What is a flush receptacle? 2. What is it used for? 3. Describe a flush receptacle. 4. How are the connections made to the terminals? 5. Describe in detail how to install a flush receptacle. Application of Knowledge Gained.— - Flush receptacles when properly installed usually cause little trouble. It is possible, how- ever, that the continued inserting and removing Of extension cord plugs may cause loosening Of the parts or connections. I Then, tOO, because Of the rapid development Of better and safer electrical arrangements, it may be desirable to replace a flush receptacle with one of a different type. References.— Willoughby, Practical Electricity for Beginners. Chap. VIII, Sec. 56; Chap. X, Sec. 81 and 84; Chap. XII, Sec. 100, 102, and 103. W illoughby, Fundamentals of H onse Wiring. Sec. 51; Figs. 19 and 20. Materials Required.— Board NO. 16, or An installation including a flush receptacle. Operations.— I. Remove the receptacle plate. 2. Disconnect the wires. 3. Remove the receptacle. 4. Install the receptacle. Parts Of 8 17111511 Receptacle 5. Attach the plate. Descriptions.— F lush receptacles are placed in steel boxes of the type used for flush switches. \Vhen the receptacle is installed, the wires are brought into the box and out the front. The receptacle is then placed in the box and attached to it by screws passing thru the openings in the metallic pieces on the front Of the receptacle. The wires are then properly prepared by removing sufficient insulation and scraping them clean, and connected to the terminals by placing them under the attaching screws. The plate is then attached by the two screws turning into tapped holes on the front Of the receptacle. TO inspect, repair, or replace this type Of receptacle is easy, the only tOOl required being a screw driver. The plate is removed readily by simply taking out the two screws that hold it in place. When this is Off, the terminals are visible and readily accessible. They may need tighten- ing or cleaning. Be sure to avoid breaking the wires because it is quite likely that it will be impossible to make new loops on them because Of their limited length. Testing Your Ability and Knowledge.— Your ability is tested by the neatness and the workability Of your installation. See if you can answer all of the questions. Did you injure the cover in any way? Did you spoil the heads Of the screws or strip the threads? Is the receptacle vertical? 3’ Are the connections made properly? Date Completed .......................... Instructor's Grade ....... . . . . . ........... . hung :55- lllluj, gag-1.1.5, red heir}; '. ll hold it If Wififlbie ii _ ELEMENTARY ELECTRICITY ‘ B-u mine" by By GEORGE A. WILLOUGHBY Published by K. G. SMITH THE MANUAL ARTS PRESS, ‘ PEORIA, ILL. LESSON SHEETS Student’s Name: ................................ Class: ......................................... Name of School: ............................... Date Begun: ................................... REMOVING, REPAIRING, REPLACING, OR RE-INSTALLING A SURFACE SNAP SWITCH What You Should Gain from This Lesson.— 7 The ability to select, use, repair, or replace surface snap switches. Questions to Be Answered.— . 1. Why is a snap switch called a surface type of switch? 2. Of what does a snap switch con- sist? 3. Where is the number of amperes capacity marked on the switch? 4. What precautions should be taken relative to the making Of the connections to the switch? 5. Describe in detail how a snap switch is installed. 6. What may be necessary if the wires are broken Off? 7. How are the working parts Of the switch exposed? References.— Willoughby, Practical Electricity for Beginners. Chap. X, Sec. 74, 75, 76, and 79. Willoughby, Fundamentals of House Wiring, Sec. 52; Figs. 51 and 52. Applications of Knowledge Gained.— Surface snap switches are used quite extensively in lighting circuits and when properly used, generally cause little trouble. It is possible, however, that after continued use they may become loose or disconnected, or perhaps broken if they are accidentally struck while stoves or furniture are being moved. Then, too, there is possibility Of the need Of replacing certain types with others more suitable and satisfactory. B-17 Materials Required.— Board No. 17, or An installation including a surface snap switch. Operations.— 1. Remove the knob from the switch stem. 2. Remove the cover. 3. Disconnect the wires. 4. Remove the switch. 5. Re-install the switch, cover, and knob. A Sun-MC Snap Switch Descriptions.— A snap switch consists Of a porcelain base upon which are mounted the terminals tO which the wires Of the circuit are connected, and the switch mechanism. Holes are provided in the base for the screws used in supporting the switch and for the wires which are connected tO the terminals. The switch itself consists, essentially, Of a copper piece SO arranged with a small spring that a turn on the knob on the end Of the shaft causes it to move to the “on” or “Off” position. The knob on the end of the shaft is removed by simply turning it in a counter-clockwise direction, or, in other words, “backwards.” The cover is Simply pulled Off. \Vhen installing a switch Of this kind, bring the wires thru the base from the under side, remove sufficient insulation, clean the wires and make the connections tO the terminals. When putting the cover into place, see that it fits the base properly. A small projection on the base and a notch in the cover must be placed together. Testing Your Ability and Knowledge.— Your ability may be tested by examining and testing out your work when completed. Neat- ness and accuracy are important factors. See if you can answer all Of the questions. Did you injure the base Of the switch by tightening the screws too much? Are the connections to the switch what they should be? Are the screws tightened sufficiently? Date Completed .......................... Instructor’s Grade ...................... . . )‘w \ w ' 1.. ‘- V3} Iflii'ill. .1. «4.: l-thtthl’v‘ ELEMENTARY ELECTRICITY B-18 Edited by ,v Published by K. G. SMITH By GEORGE A' W ILLOUGHBY THE MANUAL ARTS PRESS, PEORIA, ILL. LESSON SHEETS Student’SName:.....................‘ ........... Class: ......................................... Name Of School: ............................... Date Begun: ................................... REMOVING, REPAIRING, AND REPLACING OR RE—INSTALLING A DROP CORD What You Should Gain from This Lesson.— The ability to select, use, assemble, remove, replace, or re—install a drop-cord arrangement. Questions to Be Answered.— 1. Where are drop cords commonly used? 2. Describe a drOp cord. 3. Tell in detail how tO dismantle and assemble a drop-cord arrangement. References.— \Villoughby, Practical Electricity for Beginners. C1131). X, S€C- 75, 76’ 81’ and 82; Chap. XII, Sec. 99, 100, 103. Applications Of Knowledge Gained.— Drop cords are used quite extensively, especially in cheaper installations, and in many cases connections are made to them for using various electrical appliances such as flat-irons, heaters and washing machines. The strain sometimes brought about by these practices causes the loosening or breaking of the rosette; or the socket may be accidentally broken. In some cases it may be desirable to install a cord Of a different length from the one provided. Then, too, because of certain possible dangers, it is often well to replace brass sockets with the safer type porcelain sockets. In basements, garages, and other places where there is a possi- bility of one taking hold of a socket while in close contact with the ground, or anything con- nected to it, it is well to use porcelain sockets. 3-18 Materials Required.— Board NO. 18, or An installation including a drop cord consisting of a two-piece porcelain rosette, a cord, and a porcelain socket. Operations.— I. Remove the lower part of the rosette, the cord, and the socket from the upper part of the rosette. 2. Disconnect the wires from the rosette. 3. Disconnect the socket. 4. Reconnect the socket. 5. Reconnect the rosette. 6. Connect to the upper part of the rosette. Porcelain base and cap ' . . for drop cord. Descriptions.— . The porcelain rosette consists of two main parts, one which is attached tO the supporting surface and to which the line wires are attached, and the other to which the cord wires are connected. ‘ The parts Of the rosette can be separated by simply turning the lower part in a counter- 5 clockwise direction. The cord is made the proper length to provide for the “drop” and the making of the con- nections to the lower part Of the rosette and to the socket. To remove the rosette from the cord; loosen the terminal screws and untie the knot. TO disconnect the porcelain socket, remove the two screws, lift Off the cap, loosen the ter- minal connections, and untie the knot. To attach the socket, push the wires thru the hole in the center of the cap, tie the knot, prepare the ends of the wires, make the connections to the terminals, push the cap into place, and insert the screws. T O attach the rosette, push the cord thru the opening, tie the knot, remove sufficient insula- tion from the wires, and make the connections to the terminal screws. Testing Your Ability and Knowledge.— Your ability to assemble a drop-cord arrangement in a satisfactory manner will be shown by the results Obtained and the testing of the completed installation. See if you can answer the questions. Apply your knowledge as soon as you have an Opportunity. Are the connections to the rosette terminals made properly? Are all of the strands Of wires under the screw heads? Was the socket injured in any way? Does it fit together properly? Date Completed ....... . . . . . . . . . . . . . . . . . . . Instructor’s Grade ...................... . . auua red cap ltd. Slllr't‘ei‘l: 1 wires ‘17: a COUH'IT' of the tri- : knot. teen the 153' Ee the let"? 0 plate 9» - ',.-. if. Clt‘lll 14:1:- ill be 5h?“ r—k B-19 ELEMENTARY ELECTRICITY Kf‘c‘ileé‘m‘il'n BY GEORGE A- WILLOUGHBY THE Mfl‘filiihfnl’i pass, PEORIA, ILL. LESSON SHEETS Student’s Name: .................... _ ............ C lass* ......................................... Name of School: ............................... Date Begun: ................................... READING A KILOWATT-HOUR METER What You Should Gain from This Lesson.— The ability to read the meter which registers the power you use and also the ability to use electrical terms intelligently and to understand what they mean. Questions to Be Answered.— 3 I. What is meant by a watt? 2. What is meant by a kilowatt? 3. What is meant by a kilo- watt-hour? 4. Why. is it necessary to have such a unit as a kilowatt-hour? 5. Describe the dial of a kilowatt-hour meter. 6. How do you read a kilowatt-hour meter? 7. How should a kilo- watt—hour meter be read when one pointer is almost directly over a number? References.— Willoughby, Practical Electricity for Beginners. Chap. XI. Allen, Mechanical Devices in the Home, p. 232. Applications of Knowledge Gained.— Kilowatt-hour meters are installed in every home where electrical power is sold, to measure the power consumed. The readings of this meter are used as the basis for the charges made for the power. In most cases, a meter reader is sent at given intervals, usually once a month, to take the meter reading and the charges for power are based upon the last reading and the one previous to that. For example, an electric bill might read as follows: Meter reading Dec. 3, 1921 ........... 0173 Meter reading Nov. 3, 1921 ........... 0157 Difference . . ...................... I6 K...WH consumed . . . . .' ............ 16 9 K.W.H. @ 9c $ .81 7 K.W.H. @ 5c $ .35 Gross amount Of bill .................................... $1.10 It is Obvious that there may be times when it would be convenient for the consumer tO be able to read the meter. B-19 Materials Required.— Board NO. 19, or Kilowatt-hour meter which can be changed at will. In order to be able to practice reading, you must have an arrangement representing several meter faces upon which pointers may be set to indicate different readings. Have someone set the pointers and you take the readings. Write down the readings and have them checked. Then set the pointers as they would be for the following readings, or others given: 1451 1819 0983 An Electric Meter Testing Your Ability and Knowledge.— Your ability and knowledge can be tested by comparing readings which you take with those taken by others and by answering the questions. How many times did you have to take the readings before they were correct? Date Completed .......................... Instructor’s Grade ........................ EXHIBIT NO. g Reference material in the form of individual cards for use by the pupil doing individual work or by the teacher in giving explanations. NO. 9 MAGNET WIRE; MEASURING WIRES MAGNET WIRE. Magnet wire such as shown above is used in winding electromagnets, motors, and the like. It is available in various sizes ranging from No. 0 to NO. 40 which is about the size of a very fine thread. The various types of coverings on magnet wire include single white cotton, double white cotton, triple white cotton, single white silk, double white silk, green silk, enamel, cotton and enamel, and silk and enamel. It is available in small quantities on spools containing even pounds, halves, quarters, and eighths as well as in large quantities. Measuring Wires. The extensive use of magnet wire for rewinding coils and in various other ways where the number of the wire to be used must be known requires the measuring of wires to determine their size. The two devices which may be used for measuring wire sizes are illustrated below. WIRE GAUGE MICROMETER The wire gauge for measuring copper wires must be a Brown & Sharpe or American Standard cop- per wire gauge. Other gauges are numerous but cannot be used for this purpose. To measure with a suitable gauge, remove the covering from the wire and try it in the various slots in the gauge. The number near the slot into which it fits is the number of the wire. Measuring With a Micrometer. When measuring with a micrometer remove the covering from the wire and adjust the micrometer until the wire will just fit into the Opening. When the wire just fits into the Opening take the reading on the micrometer scales. Each Of the small divi- sions on the shaft represents .025 in. ~25 thousandths Of an inch or 25 mils— and each division on on the circular scale represents .001 in. —1 thousandth Of an inch or 1 mil. TO get the reading, count 25 for each Of the divisions on the shaft and add the reading on the circular scale. After the diameter of the wire has been determined in thousandths Of an inch or mils, the size may be deter- mined from the following table: NO. of Wire Diam. in Mils NO. of Wire Diam. in Mils 14 64.084 19 35.890 15 57.068 20 31.961 16 50.820 21 28.462 17 45.257 22 25.347 18 40.303 82 2. 3 22.571 Willoughby 25 .- ....4 x ,. find]. .é ., , No. 5 TWISTED AND PARALLEL CORDS; THEIR USES TWISTED CORD PARALLEL CORD Twisted Cord. Twisted pair lamp cord such as shown above is approved by the Underwriters for drop cords where current is controlled by a wall switch, and may be found useful in other ways. It is available in sizes of No. 18 B. & S. gauge and larger and in various colors including green- yellow, black, oak, brown, maroon, green and white. The essential points to take into considera- tion when making use of cords of this kind are the possibility of rough usage and the making of connections that are good both mechanically and electrically so no troubles will arise. Making Connections. Flexible cords are made up of strands of small wire, usually No. 30. When making connections it is essential that the covering be removed without cutting the strands of wire and that no strand is left extending beyond the terminal screws. If strands of the two wires should touch each other a short circuit would be formed. In cases where there it a possibility of rough usage or accidental pull on the cord which would . bring direct strain on the terminal screws, a knot is tied or some other means is provided for re- lieving the strain. In sockets and some plugs an Underwriters’ knot is tied to relieve this strain. Parallel Cord. Parallel lamp cord such as shown above consists of two insulated conductors laid parallel and covered with an outer braid of glazed cotton, mercerized cotton or silk. This kind of cord is approved by the Underwriters for pendant and portable use in houses, offices and stores in dry places where not subject to hard usage. It is available in various colored cover- ings, some of cotton and some of silk, including black, oak, brown, maroon, green, blue, yellow and old brass. One of the most common uses of parallel lamp cord is in connection with table lamps and floor lamps. When making up extensions for heaters, special heater cord should be used and where they will be subjected to hard usage reinforced cords should be employed. ' . Willoughby-25 No. 6. TYING AN UNDERWRITERS’ KNOT The use of Underwriters’ knots in cords in sockets and plugs is so extensive that one should be able to make these knots quickly. One can learn to do this if the instructions on this sheet are carefully followed and several knots are made . Step Number One. Untwist the cord until the ends are about one inch longer than the length desired after the knot has been tied. That is, if the ends are to be one inch long, untwist the cord two inches. Step Number Two. Holding the cord firmly between the thumb and first finger at the point to which it has been untwisted, loop one wire around the other and hold it in place by slipping it between the thumb and finger. Step Number Three. Bring the second wire ACROSS the point where the first wire crosses itself to form the loop, and then thru the loop formed by the first wire. Step Number Four. Pull both ends of the wires to tighten the knot. Willoughby-25 J No. 8. HEATER CORDS; THEIR USES. HEATER CORD. Electric heater cords of various kinds are used for connecting heating devices such as flat- irons, toasters and the like, to the source of power, or the convenience outlet. That is, they are used for making extensions for heating devices. Some cords are twisted pairs while others are twisted and have a glazed cotton covering over both wires or are parallel and with a cotton cover- ing. Good cords consist of fine wires covered with cotton, a wall of rubber compound, a heavy serving of asbestos and a plain cotton braid. A heater cord may be forced to carry much more current than that used for a lamp, hence the necessity of larger wire and additional protective covering. The asbestos covering assists in the prevention of fire if overheating should be brought about. Connecting Heater Cord to Plugs. When connecting heater cord to plugs in making up an extension or doing repair work, it is often found difficult to remove the covering without leaving ends of asbestos or other covering extending from the wires. These ends may make it difficult to tie an Underwriters’ knot or cause other inconvenience. To eliminate this difficulty the covering may be bound down with thread or held in place with a narrow piece of friction tape, as illustrated below. Connecting 3 Switch In a Heater Cord. The use of a switch in a heater cord is desirable. It eliminates the necessity of removing the plug from the convenience outlet. There are numerous switches for this purpose the one illustrated being one common type. To connect a switch of this kind in a cord the procedure should be as follows: Step One. Seperate the cap from the shell of the switch and pull out the interior of the thru cord switch. Step Two. Slip the cap on the cord. Step Three. At the point where the switch is to be located in the cord, pierce the cord thru the center with a knife for about 1 1-4 inches to separate the two wires. Step Four. Cut one wire and remove the covering for about 1-2 inch on each side of the cut but leave the covering on the other wire. Step Five. Lay the uncut wire in the groove in the switch and fasten the cut wires to the ter- minal screws. Step Six. Assemble the switch. Willoughby- 2 5 EXHIBIT NO; _:§_._ An illustration of one method of handling equipment for simple lessons. (This is a cut of the original cabinet but partly com- pleted. Cabinets are now made of sheet metal.) Cabinet g£_Electrical Equipment IDesigned for use in giving elementary instruction in pract- ica1_ applications especially where the tine limit is an important facizor. The picture shows the original cabinet of equipment as Ilsed several years ago. Cabinets used at the present time in many schools are of ShEFEt metal. The panels are of 3/8" panel stock about one ft. SQIUire. Each panel is numbered with a metal number correSponding witfll the number of the lesson. it 1;. EXHIBIT NO. 51; An instruction sheet on the making of a simple experimental motor. The finished product may be somewhat crude but it represents thought on the part of the builder and he is sure to learn several important things about electricity and magnetism in a short period of time. \‘ EXHIBIT N0. :1 Instruction sheets used as a means of imparting information to individual pupils at the time it is most needed. 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Ill Ill if); i ‘1‘ imiunmm—M .a.m:o-m-nm. 43.... ..Ii .- 0&- n r . J N. ; \ » l 4... v . A N 7 O\ .— - l g \I. . . s P I. r... .1 . ......u ... _ l o a n. . \ . N. w . . - 4 .-.. . . . . a. I ., .. w... . a L t .. t .v ..u u. . . . . ‘ . ... A ... . . u . i . W4 “ . .. ‘2...“ . . . .-s. . . . ’ ... - Q. 53$ .J. L». .. a...» ‘J . ‘1 .\ . J1- .... T v xiv ..L. O 6 (Q .\1\ Di ‘3)“ \h . . I \ ’... r.~ to. ..Iiu m N w ..o . . .tr acct. 4 -8 I ,3 .. u a J . .l r. ‘y I f I! l‘~:-‘r '-\.\;-'. L "I L l '3 l A . . c c. I.“ 1 ..LA \ L1 8 '3 K 4. U -q-fl .a’...‘ 0 e .‘3 '4 .1? ...-..t ......v is r .n. ‘y‘rxrrf‘l, .7 in...“ .... .. rat. it... .. r was...» . ......o ... 33 1.3 .... i .33.... .W. infusion!“ i-.'€3a . . ‘..« ig. h, l W‘fifis' th‘t W. “M?- 4 - . v m . :3: 3.2.5.5.... .. will. . 51...“..a .H...“ _ 7.» .U (I. . . .In. 0 u . I. . a .4 .5 ...Iu .iulan‘hlia I.-l..lv..§..u.‘.ll In}: '..’lll.i.linv.u*t.“.f4 _‘ 1 ... M .HKIF... ‘v‘ x. .9. U ,1 . U“ L an A. ... u :L. ...yu i .. . .. ‘4 . , i ‘1 A \ ; L . r _. .. . . ,. . J _ .. y ... l . II. D _ .. .. . ., .. .. . . I T. I I a A”. . a . w t .. a 1,. --.. . A . .lJ u. u .. - . r3~ EXHIBIT N0. 1, A series of sheets which may be used to advantage in presenting individual work in an elementary class such as a tryout, or finding, class. PROVIDING FOR A WALL BRACKET. (Lamp to be controlled at bracket.) Knob-end-tube. BHAC 1‘31”): 13 s'wns ours: 10*...) you saourn BE ABLE To ANSWER:- 1. What are the rules relative to running wires between studs“ 2. How are rune thru floors made? 5. How do you provide for a bracket outlet in a knob-and-tube :~: — lation? . . _-If“ ‘ \ CPBRNTIOUS:- 1- ~?»C03 and locate elect or loomebox arrengomOnto 2. Provide holes for entrance of the loom-covered wires. 5. Make necessary runs of wire. 4. make necessary connections. HELPFUL :lllul: Q :. 1. Be sure to encircle with loom the wires at the outlet. 2. Have the wires extend three or four inches beyond the loom. 5. If a loom-box is used, remove the knock-outs before puttir.' place. 4. If the fixture in to be supported by & BtUdo or stem, P31 Flace before attaching the loom-box. 5. Be sure to make proper allowane for lath uni plaster. Willuu I - .qsmsm- -. _ '““‘ _. _ 4— - 0,? } ._ ail-‘fi‘ ‘ ... 1 . O 2. 5. f ) 1;: EU ~-‘- 4. Hill. 9. 2. ."j . ‘4 . .: .11.; :‘IXTURE STUDS ; .. ‘-_ . T ..‘ «A: 05.1730“. v.1...si‘IoNs you SHOULD BE ABLE To mama:- ~.).z PROVIDING FOR.A CEILING LAMP TO BE CONTROLLED BY A SNAP SWITCH. Knob-snd-tube. JOISTS how do you provide a ceiling outlet? how do you provide a snap switch outlet? what are the rules relative to knob-and-tube wiring? RnTION33' Select and install cleats for the fixture and switch outlets. Providing openings for the loom-covered wires. make the necessary runs of wire. make the necessary connections. PEEL HINTsz' A ceiling fixture is often supported by wood screws passed thru holes near the outer edge of the canopy. Be sure to make the cleat wide enough for these. A snap switch is only about two inches in diameter. Don't make the holes in the cleat too far apart. Don‘t forget to allow for the "gripping of the plaster" when loca~ ting the cleats. Pne cleats should be toe-nailed to the Joists and studs rather .nan fastened by drtving nails thru the latter. Willoughsy-B’ ....“— __.._._...— fi‘.__ ‘ _. A»- < . __‘ ——’W;és_;.b—I -- u‘ -l- , RECEPTACLE bOA PLATE OR COVER OPERATIONS:' rELIr’FUL HINTS :" “ ‘ r 1‘ ' -V e r 1013} .LOC’J‘."5 C u' .‘ul-L: - PROVIDING FOR A FLUSH RECEPTAL (Knob-andctube.) // QUESTIONS YOU SHOULD BE ABLE TO ANSWER:- 1. What is the purpose of the steel box into which the receptacle is placed? 2. How is provision made for a flush receptacle when the knobaange tube method of wiring is used? 5. What are the rules relative to knob-and-tube wiring? Select and locate the cleats for the box. Remove the knock-outs for the entrance of the wires into Install the box. make the necessary runs of wire. Make the necessary connections. haxe the cleats sufficiently large to form a riaid 811291-70“t the box and to make their attaching easy. The lugs on the box should be placed so that the front of will extend sufficiently to come flush with the surface of the Knock-cuts for the entrance of the loom-covered wires be removed before the box is put into place. ' a receptacle is to be placed in a F wires to the point he heard has been installm. PORTILS OF RC 15 SE Flt»: 1'53 seboard, it me? ‘ _ .1. ...-.... $.31. -' ell; a, IV 7 BHUVIDING FOR AN ELECTROLIER r0 BE CONTROLLED BY'A FLUSH SWITCH. Knobsand-tube. PlJiTJ‘l UR 1507'. ELECTROLIER ”‘ ‘ 'm ’7 D‘CA‘I is U . QUESTIONS YOU SHOULD BE ABLE TO ANSWER:- 1. How do you provide for a ceiling outlet in a knob-and-tube installation? 2. now do you provide for a flush switch? 5. what is the purpose of the steel box? .. How far above the floor is the switch usually located? a. What are the important rules relative to knobzcnd-tube won; ‘ OPERATIONS:- 1. Select and locate the cleat or loom-box arrangement for the ceiling outlet. 3.3elect and locate the cleats for the switch box. . hemove the necessary knock-outs from the switch box. ' Install the switch box. ' ?° lake the necessary runs of wire. 0. Make the necessary connections. ; i,“ F, PF UL H 1231' L5 : " ‘ “ . ‘ . e 0 '~ be sure to follow carefully the rules relative to installations W Of this kind. a. Dcn'ifail to set the cleats so to allow for the gripping or "1 I . ’— vaultel. ~ "' 1 ': .- ‘ 7‘ , f“, .Iillouanby ’(1J e ~ ~-—-oflm.‘__ _ _ A q“, .... WM __._.- V. ...—fl-‘ Mu - m ' ’ ' - ' ““""‘ "um ~-——-—-—~—- . l —- ,__...‘.______ ——-- - Mm -- GI-f’. We «w ... . . -— ~- ‘ ' - . -'1’. _ .- 0 ~.. ’ fl‘ ' ' ’ " ‘ uo‘n -.-.w.‘5*"" - ruthw-m—m- ‘5'” t . v-v .- . ._. . v v -— “' 5.5.3.34". '. a": 's . _ ---~v . ‘ ' - ! E CK§VER OR PLATE ()4 h) -‘ INSTALLING AND CONNECTING A FLUSH RECEPTABLE. BOX.AND WIRING FOR A RECEPTAELE. tlBBTIONS YOU SHOULD BE ABLE TO ANSWER:- How should the connections be made to a receptacle? . Why is it necessary to hare the wires clean and bright? Why should care be taken not to leave any excess wire extending beyond the terminal connections? OPERATIONS:° 1. Prepare the wires for making the connections. 2. Install the receptacle. 5. Connect the wires to the receptacle terminals. 4. Put the cover in place. HELPFUL HINTS:- 1. 2. j. 4. When the receptacle isiinstalled, the wires are brought out the front of the box and the receptacle is attached to the box by two screws. Don't cut the wires off until after the connections have been made. Clean the wires carefully and give them one turn around the binding screws. After the screws have been turned in firmly, the ends of the wires may be broken off. Don't remove the insulating covering from the wires except at the points where the connections are made. nhen attaching the cover be careful not to injure it with the screw: driver and don‘t injure the heads of the screws. Willoughby-Qfi n . L . h. “a _. .w l mu __ , 1 INSTALLING A BRACKET . --—-—.—~ . I - . . 1'. d-W-:.~:’.lA—w—‘- "" ' WIRING PROVIDED FOR BRACKET. Note: A box,.or plate, with a stud, or stem, may be provided. -.‘.».B‘3T IONS YOU SHOULD BE ABLE TO ANSWER: how should the connections be made in installing a bracket? flow may the bracket be supported? Why is it necessary to avoid turning the socket or bracket after the connections have been made? why should the Joints be soldered and carefully taped? DruanTIONs: Prepare the wires for making the connections. ‘ grovide the necessary means of supporting the bracket. 9- “ace the connections. . Solder and tape the Joints. :. Install the bracket. 4+LPPUL HINTS:- 3 Xtures may be installed without insulating Joints When supported Wood ceilings or from lath and plaster walls or ceilings pro- . fled the WQFing is done by the knob-and-tube. 09¢n“W0rk. or ”019‘ inn. methods . . when a box or plate is provided, a stud, or stem..P1‘°Vides 3 rigid {Buns of support. In such cases a hickey is used- i‘ attacnod to the box with short stove bolts. 'hflllnnuaovn2d. .rut: .W.. , _ v 0 v ...LS tJ. The at em may .-4 Wane-«37; . ‘—.-_.-._ iv! .“;Uh- ‘R l' - . ...W M " 1 ‘ a I ' J ..4 \ w -- - #M ' . e . ...,g... EXHIBIT NO. L Samples of instruction sheets and cards suitable for use in presenting motor work. Job No. 10 INSPECTING A THREE-PHASE INDUCTION MOTOR. (SQUIRREL CAGE). Operations Necessary to perform the Job. 1. Remove the cap screws or nuts holding the heads, or ends. 2. Remove the front head. (The one opposite the pulley end.) 3. Remove the pulley end and rotor. . 4. Place the heads and rotor where they will not fall or be injured in any way. 5. Put the cap screws or nuts back into the frame or in a place where they will not be lost. 6. Note carefully the construction of the rotor. 7. Note carefully the construction of the stator. 8. Count the number of coils in the winding. 9. Count the number of slots in the stator. 10. Note the number of wires provided for connect- ing to the line. 11. Study the winding sufficiently to be able to an- swer all of the questions at the end of this lesson. Materials Required. Three-phase induction motor (squir- rel Cage type), paper and pencil for recording data. Tools Required. Wrench and screw driver. Description of Operations. . Three-phase induction motors such as illustrated in Fig. 1 are used very extensively for power purposes where Figure No. 1 three-phase current is available. Work on motors of this kind is essential because of their importance. To work intelligently requires a knowledge of the general construc- tion and arrangement of parts as well as the types of wind- ing and various other points which should be gained at this time. Removing the Heads and Rotor. The heads, or ends, of an induction motor frame are usually attached to the body of the frame with cap screws which can be removed with a wrench. The heads can then be removed with a screw- driver. The pulley end head together with the pulley and rotor can be removed intact without removing the pulley from the shaft. Care should be exercised when doing this to avoid injuring the motor in any way and the rotor should be handled carefully to avoid springing the shaft. This should be placed in a rack or in some other place where it is impossible for it to fall. The cap screws should be put back into the body or in a box so they will not be mislaid or lost. Characteristics of the Rotor. The rotor will be found to consist of steel laminations on a shaft because this material will carry varying magnetism without getting hot. There is no visible winding on the rotor but copper bars pass thru slots and are securely fastened at the ends to conducting rings which short circuit them. Any metal cylinder would revolve if placed in the position of the roter but the power of the motor would be reduced to a great extent and the motor would probably get hot. Note that there is no direct connecton between the rotor and the source of current or the winding on the stator. The rotor is said to be of the squirrel cage type because the series of bars on the cylindrical piece present the appear- ance of a squirrel cage. Figure No. 2 Characteristics of the Stator. The stator core will be found to be made up of annealed steel laminations assembled and placed in a frame. The slots will be found to contain insulating material and may be of the semi enclosed or the open type. The open type slots are used on larger machines where the coils are form wound and taped and then pushed down into the slots and held in place by wedges. The stator too is of laminated soft steel because this material will carry magnetism produced by alternating current without heat- ing. Types of Windings. The stator winding consist of coils of magnet wire placed in the slots and suitably connected for the desired results. There are several different types of windings including (1) two-layer flat diamond mush coils; (2) two-layer diamond mush pulled coils; (3) diamond coils, one side per slot and (4) basket winding. Two-layer windings with flat diamond mush coils are the most common in small motors. Mush coils differ from form wound coils in that they are not taped over their entire sur- face as those of the latter type which are forced as a whole into the slots of the stator. The ends of the coils of this type may be taped and pulled into shape after they have been put into the slots. This will make the windings close fitting at the ends. When this type of winding has been used the lower side of the coil and the upper side of another will be in the same slot all slots containing sides of two different coils. Thus the number of slots and the number of coils will be the same. Sometimes additional insulation is placed on the phase coils. Such a winding is illustrated in Fig. 2. Two-layer diamond mush pulled coils are wound in layers but are not taped. They are insulated by pieces of treated cloth triangular in shape. These coils are pulled to shape before they. are inserted into the slots and the ends will not fit to-gether as tightly as those of flat diamond mush coils. Diamond coils, one coil side per slot, may be used in which case there will be one half as many coils as slots. If the winding is of the basket type there will be one coil in each slot but the coils will not be diamond shape. If this type of winding had been used the number of slots spanned by a coil will be odd. That is, the coil pitch Wlll be 1 and 4, 1 and 6, 1 and 8, 1 and 10, etc. The number of slots must be even for this type of winding. Coil Pitch. The coil pitch is expressed as 1 and 4, 1 and 6, etc. This means that if the pitch is 1 and 6, one side of a coil will be in slot number 1 and the other side will be in slot number 6, another will be in slots 2 and 7, another in slots 3 and 8, etc. The number of slots spanned by a coil is the number included between the sides of the coil counting the first side as one. Thus if a coil is in 1 and 6 the span is 5, if it is in slots 1 and 8 the span is 7; etc. Questions 1. How can the heads and rotor be removed from the body of an induction motor frame. 2. Of what does the rotor consist? 3. Where does this type of motor get its name “squirrel cage? 4. Why are the rotor and stator made of laminated soft stee ? 5. What is the difference between an open slot and a semi enclosed slot? , 6. What type of slots were in the motor you inspected? 7. Of what does the stator winding consist? 8 Name four common types of windings? 9. What is meant by a “mush” coil? 10. What is meant by a two-layer flat diamond mush coil? coil? 11. How does a two-layer diamond mush pulled coil wind- ing differ- from a two-layer diamond mush coil winding? 12. How many slots are there in the motor you inspected? 13. How many coils are there? 14. Are there two coils sides per slot or only one? 15. What type of winding did you find on the motor you inspected? 16. What is the pitch of the coils in the motor? 17. How many wires are provided for connecting to the line? 18. List points of importance relative to the motor such as the manner in which the various coil connections are made, the way they are attached to the winding, etc. 19. Have the phase coils special insulation? 20. Are the coils mush or form wound? 21. Are the coils of the pulled type? 22. Are the coils tape all over? 23. Are the ends taped? 24. Are triagular pieces of threaded cloth used between coils? 25. Do you think a basket winding could be put on this motor ? REFERENCE CARD No. M-2 DIRECT-CURRENT MOTOR 19 Armature—including commutator. 15 Body ' 16 Field coils 17 Pole pieces 4 Brushes 00 ll sons 5 Brush springs a :. 12 Cord, Plug and binding post cover Direct-current motors such as the Robbins & Meyers illustrated above are used extensively on direct-current circuits for operating washing machines, ironing machines, and for general power purposes. Essential Parts of Direct-current Motor. The essential parts of a direct-current motor are: the armature, the commutator, the brushes, and the field. The Armature. The armature-part No. 19—consists of soft steel pieces on a shaft, and a wind- ing of magnet wire in slots provided in the core formed by the pieces, or laminations. The coils of wire are wound in a definite manner and connected to bars known as commutator bars. The operation of the motor requires a flow of electrical current thru the windings on the armature. The Commutator. The commutator on the armature shaft consists of bars of copper insulated from the shaft and from each other. The leads from the windings on the armature are connected to these bars. Electrical current to the armature coils is led in thru these commutator bars. The Brushes. The brushes— part No. 4—rub on the commutator and thus carry electricity from an outside source into the windings on the armature even tho thegarmature is revolving. The Field. The field consists of the body—part No. 15--, the field coils—part No. 16—, and the pole pieces—part No. 17. Electrical current must flow thru the coils as well as thru the winding on the armature to produce rotation. There are two ways in which the field windings and armature windings—thru the brushes-may be connected. They may be connected so that the current flows into one end of the field winding, out the other end into a brush and thru the armature windings to the other brush and then into the line. This is called series—Or both brushes may be connected to the line and both ends of the field may be connected to the line-This is called shunt. Willoughby-25 N0. M3 REPULSION INDUCTION MOTOR Net .. ' U . I | A ‘ . .1 ' ‘ u' I ‘ “ . . a ' ,, ‘0 _ ' . ' ‘ . ". iq‘. 3 '. . . - . v . t ....»M“, , . , . v . c‘ . 'I "' D I“ " ':, '—.. a .. .‘I- 'I ~ ‘ ‘ . g ‘ t - - ' .‘ '1', a . . t.‘ iv» “A x.“ ' ' ~' 1 e . ‘. ‘, l - n ' O . . . . ' J. ' l. . , v ' .. 1 ‘ l e l '- n I" V .‘w - Fig. 1 Fig. 2 The outward appearance of a typical repulsion induction motor — Robbins & Myers— is shown in Fig. 1 and the parts are shown in Fig. 2. Motors of this type are especially suitable for use on pumps, compressors and other machines where a heavy pull, or torque, is required at the start. Essential Parts of Repulsion Induction Motor. ' A motor of this type consists of a stator, an armature, brushes, and a short-circuiting device. The Stator. The stator, or stationary part, is built up of soft steel laminations secured to the frame. The windings are insulated fromthe core. The ends of the windings are brought out for connecting to the feed wires. The Armature. The armature, or revolving part, consists of a core of soft iron laminations mounted on a shaft. The coils forming the winding are carefully placed in the slots and thoroly in- sulated from the core. The windings are connected to commutator bars of copper arranged either in the form of a vertical disc or a horizontal cylinder. The bars are insulated from each other and from the shaft. The Brushes. The brushes which rub on the commutator are not connected to the feed wires but are arranged to make connections between commutator bars a given distance apart. These brushes function only when the motor is starting. The Short-circuiting Device. When single-phase alternating current is forced thru the stator windings the armature starts to revolve due to a repulsion or pushing action. After it has nearly attained its running speed the armature will function as the rotor in an induction motor if the com- mutator bars are connected together. This is done automatically by the short-circuiting device. Willoughby-25 Reference Card N 0. M-4 THREE PHASE INDUCTION MOTOR. Fig. 1. Fig. 2. Three-phase induction motors such as illustrated in Figs. 1 and 2 are used very extensively for power purposes where three-phase current is available. Motors of this type are available in sizes ranging from a fraction of a horsepower up to 40 horsepower and other types may run as high as 200 horsepower. Essential Parts of Three-phase Induction Motor. The essential parts of a three-phase in- duction motor illustrated in Fig. 2 are the stationary part or stator and the revolving part or rotor. The purpose of the other parts is to provide suitable bearings for the rotor shaft and to provide a suitable frame. ‘ The Stator. The stator of the induction motor is madelup of sheets of steel assembled and placed in the frame. It is made of sheets, or laminations, because this material will carry the varying magnetism set up in it without undue heating or loss. The stator contains the winding thru which currents from a three-phase source are forced. The three-phase currents flowing thru the winding produce a rotating magnetic field which will cause a tin can or any other metal cylinder to rotate at a given speed when placed in the opening of the stator in such a way that it is free to revolve. . The Rotor. The rotor, or revolving part of the induction motor, also consists of laminated soft steel on the shaft. There is no visible winding on this rotor but copper or other metal bars pass thru slots and are securely fastened at the ends to conducting rings which short-circuit them. This series of bars presents the appearance of a squirrel cage and hence the motor is called the squirrel cage type. Outstanding Characteristics of Induction Motor. An outstanding characteristic of this motor is that there is no external electrical connection between the rotor and stator winding; hence there is no sparking and little danger of fire. 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