Electricity Practice Name hr

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1. What is the potential difference across a 5 ohm resistor which carries a current of 5 A?

a. 100 V

b. 25 V

c. 4 V

d. 1 V

2. A superconducting wire's chief characteristic is which of the following?

a. an extremely great length

b. a large cross-sectional area

c. an extremely high temperature

d. no resistance

3. If a 75 W lightbulb operates at a voltage of 120 V, what is the current in the bulb?

a. 0.63 A

b. 1.6 A

c. 9.0 x 10 A

d. 1.1 x 10 A

4. Tripling the current in a circuit with constant resistance has the effect of changing the power by what

factor?

a. 0.33

b. 1/9

c. 3.0

d. 9.0

5. What happens to the resistance of a superconductor when its temperature drops below the critical

temperature?

a. equals that of a semiconductor of equal dimensions

b. increases by two

c. drops to zero

d. reduces to one-half

6. The unit for rate of energy transformation, the watt, in an electric circuit is dimensionally equivalent to

which of the following?

a. volt/sec

b. ampere x ohm

c. volt x ampere

d. volt/ohm

7. A wire carries a steady current of 0.1 A over a period of 20 s. What total charge passes through the wire in

this time interval?

a. 200 C

b. 20 C

c. 2.0 C

d. 0.005 C

8. If a 500 W heater carries a current of 4.0 A, what is the voltage across the ends of the heating element?

a. 2000 V

Electricity Practice Name hr

b. 125 V

c. 250 V

d. 0.008 V

9. If a 500 W heater carries a current of 4.0 A, what is the resistance of the heating element?

a. 85.7

b. 42.8

c. 31.3

d. 11.2

10. If a 500 W heater carries a current of 4.0 A, how much does it cost to operate the heater for 30 min if

electrical energy costs 6 cents per kW-hr?

a. 1.5 cents

b. 9.0 cents

c. 18.0 cents

d. 36.0 cents

11. If a lamp is measured to have a resistance of 120 ohms when it operates at a power of 100 W, what is the

applied voltage?

a. 110 V

b. 120 V

c. 125 V

d. 220 V

12. If a lamp has a resistance of 120 ohms when it operates at a power of 100 W, what current does the lamp

carry?

a. 2.10 A

b. 1.2 A

c. 0.91 A

d. 0.83 A

13. An electric toaster requires 1100 W at 110 Volts. What is the resistance of the heating coil?

a. 7.5

b. 9.0

c. 10.0

d. 11.0

14. A lightbulb has a resistance of 240 when operating at a voltage of 120 V. What is the current in the

lightbulb?

a. 2.0 A

b. 1.0 A

c. 0.5 A

d. 0.2 A

15. If a certain resistor completely obeys Ohm's law, its resistance will change

a. as the voltage across the resistor changes

b. as the current through the resistor changes

c. as the energy given off by the electrons in their collisions changes.

d. none of the above, since resistance is a constant for a given resistor.

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16. Which process will double the power given off by a resistor?

a. Doubling the current while doubling the resistance

b. Doubling the current by making a resistance half as big

c. Doubling the current by doubling the voltage

d. Doubling the current while making the voltage half as big

17. Suppose that a voltage surge produces 140 V for a moment in a 120 V line. What will temporarily be the

output of a 100 W lightbulb assuming its resistance does not change?

a. 109 W

b. 118 W

c. 127 W

d. 136 W

18. Three resistors having values of 4.0, 6.0 and 8.0 ohms, are connected in series. What is their equivalent

resistance?

a. 18.0 ohms

b. 8.0 ohms

c. 6.0 ohms

d. 1.8 ohms

19. Three resistors having values of 4.0, 6.0 and 10.0 ohms, are connected in parallel. What is their equivalent

resistance?

a. 20.0 ohms

b. 7.3 ohms

c. 6.0 ohms

d. 1.9 ohms

20. Three resistors connected in parallel have individual values of 4.0, 6.0 and 10.0 ohms, respectively. If this

circuit is connected to a 12.0 V battery what is the current in the 10 ohm resistor?

a. 0.55 A

b. 5.2 A

c. 1.2 A

d. 2.0 A

21. Three resistors connected in parallel have individual values of 4.0, 6.0 and 10.0 ohms, respectively. If this

combination is connected in series with a 12.0 V battery and a 2.0 ohm resistor, what is the current in the 10

ohm resistor?

a. 0.59 A

b. 1.0 A

c. 11.2 A

d. 16.0 A

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22. The following three appliances are connected in parallel to a 120 volt house circuit:

i) toaster, 1200 W,

ii) coffee pot, 750 W, and

iii) microwave, 600 W.

If all were operated at the same time what total current would they draw?

a. 3 A

b. 5 A

c. 10 A

d. 21 A

23. Three resistors, with values of 3, 6 and 12 ohms, respectively, are connected in parallel. What is the

overall resistance of this combination?

a. 0.58 ohms

b. 1.7 ohms

c. 7.0 ohms

d. 21.0 ohms

24. Two resistors of values 6 and 12 ohms are connected in parallel. This combination in turn is hooked in

series with a 4 ohm resistor. What is the overall resistance of this combination?

a. 0.5 ohms

b. 2.0 ohms

c. 8.0 ohms

d. 22.0 ohms

25. Two resistors of values 6 and 12 ohms are connected in parallel. This combination in turn is hooked in

series with a 2 ohm resistor and a 24 V battery. What is the current in the 2 ohm resistor?

a. 2.0 A

b. 4.0 A

c. 6.0 A

d. 12.0 A

26. Four 1.5 volt AA batteries in series are used to power a transistor radio. If the batteries hold a total charge

of 240 C, how long will they last if the radio has a resistance of 200 Ω ?

a. 1.1 hours

b. 2.2 hours

c. 4.1 hours

d. 13 hours

27. What is the maximum number of 100 Watt lightbulbs you can connect in parallel in a 120 V home circuit

without burning out the 20 A fuse?

a. 11 bulbs

b. 17 bulbs

c. 23 bulbs

d. 29 bulbs

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28. In a circuit, a current of 1.0 A is drawn from a battery. The current then divides and passes through two

resistors in parallel. One of the resistors has a value of 64 Ω and the current through it is 0.2 A. What is the

value of the other resistor?

a. 8 Ω

b. 16 Ω

c. 24 Ω

d. 32 Ω