Chapter 3 - Ohm’s Law - Grob's Basic Electronics 13th

With 24 V across a 1-kΩ resistor, the current, I, equals: a. 0.24 A. b. 2.4 mA. c. 24 mA. d. 24 µA.

c

With 30 µA of current in a 120-kΩ resistor, the voltage, V, equals: a. 360 mV. b. 3.6 kV. c. 0.036 V. d. 3.6 V.

d

How much is the resistance in a circuit if 15 V of potential difference produces 500 µA of current? a. 30 kΩ. b. 3 MΩ. c. 300 kΩ. d. 3 kΩ.

a

A current of 1000 µA equals: a. 1 A. b. 1 mA. c. 0.01 A. d. none of the above.

b

One horsepower equals: a. 746 W. b. 550 ft·lb/s. c. approximately 3/4 kW. d. all of the above.

d

With R constant: a. I and P are inversely related. b. V and I are directly proportional. c. V and I are inversely proportional. d. none of the above.

b

One watt of power equals: a. 1 V × 1 A. b. 1 J/s. c. 1 C/s. d. both a and b.

d

A 10-Ω resistor dissipates 1 W of power when connected to a DC voltage source. If the value of DC voltage is doubled, the resistor will dissipate: a. 1 W. b. 2 W. c. 4 W. d. 10 W.

c

If the voltage across a variable resistance is held constant, the current, I, is: a. inversely proportional to resistance. b. directly proportional to resistance. c. the same for all values of resistance. d. both a and b.

a

A resistor must provide a voltage drop of 27 V when the current is 10 mA. Which of the following resistors will provide the required resistance and appropriate wattage rating? a. 2.7 kΩ, 1/8 W. b. 270 Ω, 1/2 W. c. 2.7 kΩ, 1/2 W. d. 2.7 kΩ, 1/4 W.

c

The resistance of an open circuit is: a. approximately 0 Ω. b. infinitely high. c. very low. d. none of the above.

b

The current in an open circuit is: a. normally very high because the resistance of an open circuit is 0 Ω. b. usually high enough to blow the circuit fuse. c. zero. d. slightly below normal.

c

Which of the following safety rules should be observed while working on a live electric circuit? a. Keep yourself well insulated from earth ground. b. When making measurements in a live circuit place one hand behind your back or in your pocket. c. Make resistance measurements only in a live circuit. d. Both a and b.

d

How much current does a 75-W lightbulb draw from the 120-V power line? a. 625 mA. b. 1.6 A. c. 160 mA. d. 62.5 mA.

a

The resistance of a short circuit is: a. infinitely high. b. very high. c. usually above 1 kΩ. d. approximately zero.

d

Which of the following is considered a linear resistance? a. lightbulb. b. thermistor. c. 1-kΩ, ½-W carbon-film resistor. d. both a and b.

c

How much will it cost to operate a 4-kW air-conditioner for 12 hours if the cost of electricity is 12¢/kWh? a. $5.76. b. 57.6¢. c. $576. d. $4.80.

a

What is the maximum voltage a 150-Ω, 1/8-W resistor can safely handle without exceeding its power rating? (Assume no power rating safety factor.) a. 18.75 V. b. 4.33 V. c. 6.1 V. d. 150 V.

b

Which of the following voltages provides the greatest danger in terms of electric shock? a. 12 V. b. 10,000 mV. c. 120 V. d. 9 V.

c

If a short circuit is placed across the leads of a resistor, the current in the resistor itself would be: a. zero. b. much higher than normal. c. the same as normal. d. excessively high.

a