1. A positive electric pole
(a) has a deficiency of electrons.
(b) has fewer electrons than the negative pole.
(c) has an excess of electrons.
(d) has more electrons than the negative pole.
2. An EMF of 1 V
(a) cannot drive much current through a circuit.
(b) represents a low resistance.
(c) can sometimes produce a large current.
(d) drops to zero in a short time.
3. A potentially lethal electric current is on the order of
(a) 0.01 mA.
(b) 0.1 mA.
(c) 1 mA.
(d) 0.1 A.
4. A current of 25 A is most likely drawn by
(a) a flashlight bulb.
(b) a typical household.
(c) a utility power plant.
(d) a small radio set.
5. A piece of wire has a conductance of 20 S. Its resistance is
(a) 20 Ω.
(b) 0.5 Ω.
(c) 0.05 Ω.
(d) 0.02 Ω.
6. A resistor has a value of 300 Ω. Its conductance is
(a) 3.33 mS.
(b) 33.3 mS.
(c) 333 μS.
(d) 0.333 S.
7. A span of wire 1 km long has a conductance of 0.6 S. What is the conductance of a span of this same wire that is 3 km long?
(a) 1.8 S
(b) 0.6 S
(c) 0.2 S
(d) More information is necessary to determine this.
8. Approximately how much current can a 2-kW generator reliably deliver at 117 V?
(a) 17 mA
(b) 234 mA
(c) 17 A
(d) 234 A
9. A circuit breaker is rated for 15 A at 117 V. Approximately how much power does this represent?
(a) 1.76 kW
(b) 1760 kW
(c) 7.8 kW
(d) 0.0078 kW
10. You are told that an air conditioner has cooled a room by 500 Btu over a certain period of time. What is this amount of energy in kWh?
(a) 147 kWh
(b) 14.7 kWh
(c) 1.47 kWh
(d) 0.147 kWh
11. Of the following energy units, the one most often used to define electrical energy is
(a) the Btu.
(b) the erg.
(c) the foot-pound.
(d) the kilowatt-hour.
12. The frequency of common household ac in the United States is
(a) 60 Hz.
(b) 120 Hz.
(c) 50 Hz.
(d) 100 Hz.
13. Half-wave rectification means that
(a) half of the ac wave is inverted.
(b) half of the ac wave is cut off.
(c) the whole ac wave is inverted.
(d) the effective voltage is half the peak voltage.
14. In the output of a half-wave rectifier,
(a) half of the ac input wave is inverted.
(b) the effective voltage is less than that of the ac input wave.
(c) the effective voltage is the same as that of the ac input wave.
(d) the effective voltage is more than that of the ac input wave.
15. In the output of a full-wave rectifier,
(a) half of the ac input wave is inverted.
(b) the effective voltage is less than that of the ac input wave.
(c) the effective voltage is the same as that of the ac input wave.
(d) the effective voltage is more than that of the ac input wave.
16. A low voltage, such as 12 V,
(a) is never dangerous.
(b) is always dangerous.
(c) is dangerous if it is ac, but not if it is dc.
(d) can be dangerous under certain conditions.
17. Which of the following units can represent magnetomotive force?
(a) The volt-turn
(b) The ampere-turn
(c) The gauss
(d) The gauss-turn
18. Which of the following units can represent magnetic flux density?
(a) The volt-turn(b) The ampere-turn
(c) The gauss
(d) The gauss-turn
19. A ferromagnetic material
(a) concentrates magnetic flux lines within itself.
(b) increases the total magnetomotive force around a current-carrying wire.
(c) causes an increase in the current in a wire.
(d) increases the number of ampere-turns in a wire.
20. A coil has 500 turns and carries 75 mA of current. The magnetomotive force is
(a) 37,500 At.(b) 375 At.
(c) 37.5 At.
(d) 3.75 At.
1. b 2. c 3. d 4. b 5. c 6. a 7. c 8. c 9. a 10. d 11. d 12. a 13. b 14. b 15. c 16. d 17. b 18. c 19. a 20. c
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