OHM'S LAW QUIZ

A 120 V lamp-dimming circuit is controlled by a rheostat and protected from excessive current by a 3 A fuse. To what minimum resistance value can the rheostat be set without blowing the fuse? Assume a lamp resistance of 20 ohms.

4

2

40

20

TRUE ANSWER : ?
YOUR ANSWER : ?

Twelve volts are applied across a resistor. A current of 3 mA is measured. What is the value of the resistor?

4.4

4 k

4

400

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You are measuring the current in a circuit that is operated on an 18 V battery. The ammeter reads 40 mA. Later you notice the current has dropped to 20 mA. How much has the voltage changed?

18 V

0 V

900 mV

9 V

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What is the approximate filament resistance of a light bulb if it operates from a 110 V source and 0.6 A of current is flowing?

6.6

66

183

18.3

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If you wish to increase the amount of current in a resistor from 120 mA to 160 mA by changing the 24 V source, what should the new voltage setting be?

3.2 V

320 V

32 V

8 V

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Four amperes of current are measured through a 24 resistor connected across a voltage source. How much voltage does the source produce?

96 V

8 V

960 V

9.6 V

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How much resistance is needed to draw 17.6 mA from a 12 volt source?

212

680

68

6.8 k

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A current of 200 µA through a 6.8 k resistor produces a voltage drop of

1.36 V

340 V

13.6 V

34.4 V

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The current through a flashlight bulb is 40 mA and the total battery voltage is 4.5 V. The resistance of the bulb is approximately

1.2

112

11.2

18

TRUE ANSWER : ?
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What is the approximate resistance of a rheostat if the voltage source is 18 V and the current is 220 mA?

8.2

820

8.2 k

82

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