(1) What is Ohm's law?

(2) How would you define "drop of potential"?

(3) What are the three methods of connecting incandescent lamps in circuit?

(4) What are the units employed in measurement of current, electromotive force, and resistance?

(5) What is an electromagnet?

(6) What is the distinguishing feature of the closed-circuit burglar-alarm system?

(7) A group of 30 lamps, 16 candlepower, 110 volts, is located 100 feet from the source of current supply. If the drop in potential is 1 1/4 volts, what size of wire should be used? Ans. No. 6 B. & S.

(8) What is the difference between series and parallel arrangement of conductors?

(9) If the resistance of a wire 3,540 feet long is 2,917 ohms, what is the size of the wire?

(10) What is a safety cut-out?

(11) What methods are ordinarily used in the production of electric current?

(12) What is the area in circular mils of a wire 6| inches in diameter? Ans. 40,640,625 circ. mils.

(13) A group of lamps is composed of 3 of 50 candle-power, 8 of 32 candlepower, and 32 of 16 candlepower, all supplied from a 110-volt circuit. What will be the size of feeders, the distance being 340 feet, and the drop 5 volts?

Ans. No. 4B.&S.

(14) What method is employed in testing the insulation resistance of house circuits during installation?

(15) Under what circumstances are automatic drops installed on bell circuits?

(16) Explain the action of a pendant burner for electric gas lighting.

(17) A current of 13.5 amperes is to be transmitted to a bank of 110-volt lamps, distant 320 feet, with 5 per cent. loss in line. (a) What will be the resistance of the two conductors? (b) What is the resistance per foot, assuming each conductor to be 320 feet long?


(a) .43 ohm. (b) .00067 ohm.

(18) Under what circumstances may single-pole switches be used in a lighting system?

(19) Describe briefly the closet system of house wiring.

(20) What size of conductor is required for a 110-volt circuit, 540 feet in length from dynamo to lamps, when sixty-five 16-candlepower lamps are used and a drop in potential of 4.5 volts is allowed? Ans. No. 1 B. & S.

(21) What is the special advantage of the three-wire system?

(22) Make a rough sketch showing the different parts of an electric bell, and the path of the current through it.

(23) What apparatus is required to operate electric gas-lighting attachments on the parallel system?

(24) What will be the drop of potential in a 110-volt circuit having 45 lamps of 16 candlepower and 4 lamps of 32 candlepower, the distance from the dynamo being 105 feet, and the wire No. 6 B. & S.? Ans. 3.59 volts.

(25) What is the principle underlying the use of the loop circuit?

(26) To what classes of installation are cleat work, molding, and concealed work, respectively, best suited?

(27) It is proposed to supply current, by means of a No. 8 wire, to thirty-six 32-candlepower lamps mounted on a chandelier at a distance of 75 feet from the distributing box, the allowable loss being 3.5 volts. Will this size of wire be correct? Give reasons for your answer.

(28) What consideration should apply in deciding upon the location of the distributing boxes for inside electric-light wiring?

(29) What alteration is necessary to a vibrating bell in order to change it to one giving a single stroke?

(30) What size of wire is generally used in annunciator work (a) for the leading wires? (b) for the battery wire?

(31) What size of wire is necessary for a 110-volt loop circuit around the walls of a room 45 feet long by 38 feet broad, thirty-two 16-candlepower lamps being used, and a drop of 1 1/2 per cent. being allowed? Ans. No. 8 B. & S.

(32) In what class of work is the megohm used?

(33) What precautions should be taken when electric-light wires are passed through a wall or partition?

(34) A cluster of lights, consisting of ten 16-candlepower lamps and three 32-candlepower lamps, is installed on a 55-volt circuit. A line loss of 2.5 per cent. is allowed, the length of line from closet to lamps being 110 feet. What size of wire must be used? Ans. No. 6 B. & S.

(35) Explain the action of a buzzer.

(36) What arrangement may be used to give notice of a short circuit on a gas-lighting system operated by a battery?

(37) The feeders in a 110-volt lighting circuit are 135 feet in length, and supply current to two hundred and forty 16-candlepower lamps, with a drop of 2 volts. What is the size of conductor in circular mils? Ans. 174,960 circ. mils.

(38) What are the respective advantages of acid and resin as a soldering flux?

(39) What is the object of the neutral wire in the three-wire system?

(40) A feeder 225 feet long, No. 6 wire, supplies current to twenty-five 16-candlepower 55-volt lamps. Disregarding heating effect, what would be the drop of potential on the line? Ans. 4.625 volts.

(41) How would you proceed in installing a battery of two or three cells, for bellwork, if the cells are delivered to you in the original package, as shipped?

(42) In wiring for the multiple system of electric gas lighting, what special precautions must be observed?

(43) What means should be employed to take the strain off the connections of a lamp cord inside of a rosette?

(44) What will be the drop of potential in a 110-volt circuit, having 46 lamps of 16 candlepower, the conductor being No. 4 wire, and its length for the single distance 84 feet?

Ans. 1 volt.

(45) If it is desired to ring bells from a lighting circuit, what arrangements must be made to secure this result?

(46) What is the distinction between a feeder and a main?

(47) A hall dome 120 feet in diameter is fitted with 40 lamps, of 50 candlepower each, spaced at equal distances apart in loop circuit. The E. M. F. of the system is 110 volts, and current is supplied at one side of the circle by feeders 85 feet long. Allowing for a drop of 1 1/4 volts in the feeders, and 2.5 volts in the lamp circuit, what size of wire should be used in each case?


No. 1 wire for the feeder.

No. 0 wire for the lamp circuit.

(48) Show by means of diagrams the methods of lamp connection in the multiple-arc, the multiple-series, and three-wire systems.

(49) What size of wire will be required for an installation on the three-wire system, having sixty-six 110-volt 16-can-dlepower lamps, the distance between these and the point of supply being 180 feet, and a drop of 2.5 volts being allowed?

Ans. No. 6 wire.

(50) When two or more bells are connected in series, what changes, if any, are necessary in their construction?

(51) When is it advisable to install the flexible two-wire system in a building?

(52) The feeders passing through a building are 80 feet long, and supply current to four hundred and eighty 16-can-dlepower 110-volt lamps. What size must these conductors be, if the drop of potential is not to exceed 1.25 per cent. ?

Ans. 296,000 circ. mils.

(53) Show, by means of a diagram, a method of ringing a bell from either one of two different points.

(54) What will be the drop in voltage on a 55-volt circuit when a loss of 4.6 per cent. is allowed? Ans. 2.65 volts.

(55) Explain the object of a drip loop in house wiring.

(56) An installation on the three-wire system has eighty-four 16-candlepower 110-volt lamps on a circuit 320 feet long, a loss of 3 per cent. being allowed. What size of conductor is required? Ans. No. 4 B. & S.