Question 1

Which of the following best describes electric current in a conductor?

Accepted Answer

The rate at which charge flows through a cross-sectional area.

Question 2

A copper wire has a resistance $$R at $$room temperature. If the wire is stretched to twice its original length without changing its volume, what will be its new resistance?

Accepted Answer

$$2R$$

Question 3

Which equation correctly expresses Ohm’s Law?

Accepted Answer

$$V = IR$$

Question 4

A resistor with resistance $$R is $$connected in series with another resistor of resistance $$2R. $$What is the equivalent resistance of the combination?

Accepted Answer

$$3R$$

Question 5

If three resistors of $$6\ \Omega$$, $$3\ \Omega$$, and $$2\ \Omega$$ are connected in parallel, what is the equivalent resistance?

Accepted Answer

$$1.09\ \Omega$$

Question 6

Which of the following statements about resistivity is correct?

Accepted Answer

Resistivity is a property of the material and is independent of its dimensions.

Question 7

A current of $$2\ \mathrm{A}$$ flows through a $$10\ \Omega$$ resistor. What is the potential difference across the resistor?

Accepted Answer

$$20\ \mathrm{V}$$

Question 8

Which of the following best describes the effect of increasing temperature on the resistance of a typical metallic conductor?

Accepted Answer

Resistance increases.

Question 9

A device obeys Ohm’s Law if:

Accepted Answer

The current through it is directly proportional to the voltage across it.

Question 10

A $$12\ \mathrm{V}$$ battery is connected to a circuit with a total resistance of $$4\ \Omega. $$What is the current supplied by the battery?

Accepted Answer

$$3\ \mathrm{A}$$

Question 11

Which of the following is the correct formula for the resistance $$R of a $$wire in terms of its resistivity $$\rho$$, length $$L$$, and cross-sectional area $$A$$?

Accepted Answer

$$R = \rho \dfrac{L}{A}$$

Question 12

If a $$100\ \mathrm{W}$$ light bulb operates at $$120\ \mathrm{V}$$, what is the resistance of the bulb when it is on?

Accepted Answer

$$144\ \Omega$$

Question 13

A circuit contains two resistors, $$R_1 = 5$$\ \Omega$$ and R_2$ = 10\ \Omega$$, connected in parallel. What is the total resistance?

Accepted Answer

$$3.33\ \Omega$$

Question 14

A wire of length $$L$$ and cross-sectional area $$A$$ has resistance $$R. If $$both the length and area are doubled, what happens to the resistance?

Accepted Answer

It remains the same.

Question 15

Which of the following is a correct statement of Ohm’s 2nd Law (microscopic form)?

Accepted Answer

$$\vec{J} = \sigma \vec{E}$$

Question 16

A toaster rated at $$1200\ \mathrm{W} is $$plugged into a $$120\ \mathrm{V}$$ outlet. What current does it draw?

Accepted Answer

$$10\ \mathrm{A}$$

Question 17

A student connects three identical resistors in series to a battery. If the total current in the circuit is $$I$$, what is the current through each resistor?

Accepted Answer

$$I$$

Question 18

A $$9\ \mathrm{V}$$ battery is connected to a resistor, and a current of $$0.3\ \mathrm{A}$$ flows. What is the resistance?

Accepted Answer

$$30\ \Omega$$

Question 19

Which of the following is a real-world application of resistors in parallel?

Accepted Answer

Household electrical wiring, where multiple appliances operate independently.

Question 20

A wire has a resistance of $$5\ \Omega at$$ $$20^\circ\mathrm{C}. If $$the temperature coefficient of resistance is $$0.004/ ^\circ\mathrm{C}$$, what is the resistance at $$70^\circ\mathrm{C}$$?

Accepted Answer

$$6\ \Omega$$

Electric Current, Resistance, and Ohm’s Laws

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