Q: A circuit contains a $$10\ \Omega$$ resistor and a $$20\ \Omega$$ resistor in series. What is the total resistance?

$$R_{\text{total}} = 10 + 20 = 30\ \Omega$$

Question 1

A light bulb is connected to a battery in a simple circuit. If the battery provides a voltage $$V$$ and the bulb has resistance $$R$$, what is the current $$I$$ flowing through the bulb?

Accepted Answer

$$I = \frac{V}{R}$$

Question 2

Which of the following best describes the function of a fuse in an electrical circuit?

Accepted Answer

It opens the circuit when the current exceeds a safe value.

Question 3

A toaster is rated at $$1200\ \mathrm{W}$$ and operates at $$120\ \mathrm{V}. $$What is the current drawn by the toaster?

Accepted Answer

$$I = \frac{P}{V} = \frac{1200}{120} = 10\ \mathrm{A}$$

Question 4

Which equation correctly relates electrical power $$P$$, current $$I$$, and resistance $$R$$?

Accepted Answer

$$P = I^2$ R$$

Question 5

A wire has a resistance $$R. If $$the wire is replaced with another wire of the same material but twice the length and half the cross-sectional area, what happens to the resistance?

Accepted Answer

The resistance increases by a factor of 4.

Question 6

Which of the following statements about alternating current (AC) is correct?

Accepted Answer

AC reverses direction periodically, typically in a sinusoidal pattern.

Question 7

A circuit contains a $$10\ \Omega$$ resistor and a $$20\ \Omega$$ resistor in series. What is the total resistance?

Accepted Answer

$$R_{	ext{total}} = 10 + 20 = 30\ \Omega$$

Question 8

If a $$60\ \mathrm{W}$$ light bulb is connected to a $$120\ \mathrm{V}$$ supply, what is the resistance of the bulb?

Accepted Answer

$$R = \frac{V^2$}{P} = \frac{120^2$}{60} = 240\ \Omega$$

Question 9

Which device is used to manually open or close a circuit, allowing or stopping the flow of current?

Accepted Answer

Switch

Question 10

A circuit breaker is designed to protect electrical circuits from damage caused by:

Accepted Answer

Excess current

Question 11

Which formula gives the power dissipated in a resistor when a current $$I$$ flows through it and the voltage across it is $$V$$?

Accepted Answer

$$P = IV$$

Question 12

A $$100\ \Omega$$ resistor is connected to a $$10\ \mathrm{V}$$ battery. How much power is dissipated by the resistor?

Accepted Answer

$$P = \frac{V^2$}{R} = \frac{10^2$}{100} = 1\ \mathrm{W}$$

Question 13

Which of the following statements about direct current (DC) is correct?

Accepted Answer

DC flows in one direction only.

Question 14

A household circuit is protected by a $$15\ \mathrm{A}$$ fuse. If an appliance draws $$20\ \mathrm{A}$$, what will happen?

Accepted Answer

The fuse will blow, opening the circuit.

Question 15

If the current in a wire is doubled, what happens to the power dissipated in the wire (assuming resistance stays constant)?

Accepted Answer

Power increases by a factor of 4.

Question 16

Which of the following is a correct unit for electrical power?

Accepted Answer

Watt ($$\mathrm{W})$$

Question 17

A $$12\ \mathrm{V}$$ battery supplies $$3\ \mathrm{A} of $$current to a circuit. What is the total power supplied?

Accepted Answer

$$P = IV = 12 	imes 3 = 36\ \mathrm{W}$$

Question 18

Which of the following would decrease the resistance of a wire?

Accepted Answer

Increasing the cross-sectional area

Question 19

A $$5\ \Omega$$ and a $$10\ \Omega$$ resistor are connected in parallel. What is the total resistance?

Accepted Answer

$$R_{	ext{total}} = \frac{1}{\frac{1}{5} + \frac{1}{10}} = \frac{10}{3} \approx 3.33\ \Omega$$

Electric Circuits and Current: Study Notes

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