

Electricity  Basic Navy Training Courses NAVPERS 10548 
Here is the "Electrician's Mate 3  Navy Training Courses"
(NAVPERS 10548) in its entirety (or will be eventually). It should provide one of
the Internet's best resources for people seeking a basic electricity course  complete
with examples worked out. See
copyright.
See Table of Contents.
¶ U.S. GOVERNMENT PRINTING OFFICE;
1949
CHAPTER 1 QUIZ
ELECTRICAL CURRENTS AND CIRCUITS  OHM'S LAW ELECTRICITY
1. The unit of electrical pressure is the _____________.
2. The unit of electrical current is the
_____________.
3. The unit of electrical resistance is the _____________.
4. The current in a circuit is (a) _____________ proportional to the applied voltage.
(b) _____________ proportional to the resistance.
5. The relation between current, voltage and resistance
in a circuit is expressed by the equation Amperes _____________.
6. If a generator
supplies 60 volts across a resistor and a current of 10 amperes flows through the circuit, what is the
ohmic value of the resistor?
7. A generator is supplying 120 volts to a circuit which comprises two
resistances, 6 ohms and 4 ohms, in series. What is the current flowing in the circuit?
8. What
voltage must a generator have to produce a current of 6 amperes through resistances of 2 ohms, 3 ohms, and
5 ohms connected in series?
9. Four resistors, of 8 ohms, 6 ohms, 2 ohms and one of unknown resistance, are
connected in series. A generator supplies 120 volts across this circuit. The IRdrop across the 6ohm
resistance is 36 volts. (a) What current is flowing in the circuit? (b) What is the total circuit
resistance? (c) What ohmic value has the unknown resistor?
10. A generator supplies 100 volts to 3
resistors in series, whose resistances are 2 ohms, 3 ohms and 5 ohms. (a) What current flows in the
circuit? (b) What is the current in each resistor?
11. Find the current that would flow in a
circuit of 6 ohms and 8 ohms connected in series, if 140 volts were impressed on the circuit.
12. A generator furnishes 100 volts to a group of 3 resistors connected in parallel. One resistor is
7 ohms, another 2 ohms, and the third 1 ohm. (a) What current flows in each resistor? (b) What is the
total current flowing in the circuit? (c) What is the equivalent resistance of all 3 resistors in
parallel?
13. A current of 10 amperes flows in a circuit containing 2 resistances in parallel, one
12 ohms and the other 6 ohms. What is the voltage impressed on the circuit?
14. A generator is supplying 10
amperes to a 5ohm resistor and an unknown resistor in parallel. If 8 amperes flows through the 5ohm
resistor, what is the ohmic value of the unknown resistor?
15. Four resistors are connected in
parallel. One is 12 ohms, one is 4 ohms, and the other two are unknown. The current through one unknown
resistor is 12 amperes and through the other unknown 20 amperes when this combination is put across a
120volt generator. (a) What is the total current the generator supplies to the circuit
(b) What is the total power consumed in the circuit? (c). How much power is used up in each resistor?
16. A generator supplies 150 volts to 3 resistances in parallel. One resistor is 50 ohms, one 75 ohms, and
the third is unknown. (a) If 5 amperes flows through the unknown resistor, what is its resistance?
(b) How much power is expended in each resistor? (c) How much power is taken by the whole circuit?
17. A generator expends 2,880 watts when supplying a current of 12 amperes to a circuit consisting of
3 resistances in parallel. One is 60 ohms, another 40 ohms, and the third unknown. What is the ohmic
value of the unknown resistance?
18. A 35ohm resistor is in series with a parallel group which
contains a 50ohm resistor, a 30ohm resistor and an unknown resistor. If the total resistance of the
circuit is 50 ohms, what is the ohmic value of the unknown resistor?
19. An unknown resistor is
placed in series with two other resistances connected in parallel. One is 5 ohms, the other one is 20
ohms. This combination of three resistances is in parallel with one of 50 ohms. If 120 volts is impressed
on the circuit and 10 amperes flows, what is the ohmic value of the unknown resistor?
20. Three
groups of resistances are connected in series. The first group contains 20 ohms and 30 ohms in parallel.
The second group contains 6 ohms and an unknown in parallel. The third group contains 40 ohms and 60 ohms
in parallel. If 120 volts is impressed on the circuit and 3 amperes flow, what is the ohmic value of the
unknown resistor?
21. What voltage must a generator have in order to force 20 amperes through a 2ohm
resistor in series with a parallel group of two others having resistances of 3 ohms and 6 ohms?
22. How much power is expended by a generator that furnishes 130 volts to the following three groups of
resistances connected in series? The first group contains 5 ohms and 20 ohms in parallel. The second
group contains a 6ohm resistor. The third group contains 4 ohms and 12 ohms in parallel.
23. A
generator supplies 120 volts to a lighting circuit. A group of lamps connected in parallel across the
line, nearest the generator, contains two lamps in parallel. A second group also across the line contains
three lamps in parallel. The resistance of each side of the line from the generator to the first group of
lamps is 0.4 ohm. The resistance of each side of the line between the first group of lamps and the second
group is 0.5 ohm. Find the voltage across each group of lamps if each lamp draws 1 ampere.
24.
Fill in the blanks below with the appropriate word to make each sentence a true statement.
(a) The electrical energy used up in forcing a current through a conductor is transformed into
_____________. (b) The electrical energy used up each second in forcing electrons through a
conductor depends on the _____________ of the conductor. (c) The electrical energy
used up each second in forcing electrons through a conductor depends on the square of the
_____________. (d) A slight overload will produce a _____________ increase in heating.
25.
How does overheating of a conductor affect the insulation around it?
CHAPTER 1 ANSWERS
ELECTRICAL CURRENTS AND CIRCUITS  OHM'S LAW ELECTRICITY
1. volt
2. ampere
3. ohm
4. (a) directly (b) inversely
5. volts/ohms
6. 6 ohms
7. 12 amperes
8. 60 volts
9. (a) I = 6 amperes (b) R_{t} = 20 ohms (c) R_{x} = 20
ohms
10. (a) I = 10 amperes (b) I = 10 amperes
11. I = 10 amperes
12. (a) I_{R7} = 14.28 I_{R2} = 50.00 I_{R1}
= 100.00 (b) I_{T} = 164.28 amperes (c) R_{T} = 100/164.3 = 0.608 ohms
13. E = 40 volts
14. R = 20 ohms
15. (a) I_{T}
= 72 amperes (b) P_{T} = 8640 watts (c) P_{R12} = 1200 watts P_{R4}
= 3600 watts P_{I12}
= 1440 watts P_{I20} = 2400 watts
16. (a) R_{x}
= 30 ohms (b) P_{x} = 750 watts P_{50} = 450 watts P_{75}
= 300 watts (c) P_{T} = 1500 watts
17. R_{x} = 120 ohms 18. R_{x}
= 75 ohms 19. R_{x} = 11.80 ohms
20. R = 12 ohms
21. E = 80 volts
22. P = 1300 watts
23. Across 2lamp group, E = 116
volts Across 3lamp group, E = 113 volts
24. (a) heat (b) resistance (c) current (d) great
25. Overheating chars and breaks down the insulation



