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
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.
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 IR-drop across the
6-ohm 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 5-ohm resistor and an unknown resistor
in parallel. If 8 amperes flows through the 5-ohm 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 120-volt 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 un-known.
(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 35-ohm resistor is in series with a parallel group which contains a 50-ohm resistor,
a 30-ohm 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 2-ohm
resistor in series with a parallel group of two others having resistances of 3 ohms and
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 6-ohm 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
(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
4. (a) directly
6. 6 ohms
7. 12 amperes
8. 60 volts
9. (a) I = 6 amperes
= 20 ohms
(c) Rx = 20 ohms
10. (a) I = 10 amperes
(b) I = 10 amperes
11. I = 10 amperes
12. (a) IR7 = 14.28
IR2 = 50.00
IR1 = 100.00
(b) IT = 164.28 amperes
(c) RT = 100/164.3 = 0.608
13. E = 40 volts
14. R = 20 ohms
15. (a) IT = 72 amperes
= 8640 watts
(c) PR12 = 1200 watts
PR4 = 3600 watts
PI12 = 1440 watts
PI20 = 2400 watts
16. (a) Rx = 30 ohms
= 750 watts
P50 = 450 watts
P75 = 300 watts
(c) PT = 1500 watts
17. Rx = 120 ohms
18. Rx = 75 ohms
19. Rx = 11.80 ohms
20. R = 12 ohms
21. E = 80 volts
22. P = 1300 watts
23. Across 2-lamp group, E = 116 volts
3-lamp group, E = 113 volts
24. (a) heat
25. Overheating chars and breaks down the insulation