Question 1

Which of the following best describes Ohm's Law for a metallic conductor at constant temperature?

Accepted Answer

The current through the conductor is proportional to the voltage across it: $$V = IR.$$

Question 2

A wire of length $$L$$ and cross-sectional area $$A$$ has resistance $$R. If $$the wire is replaced by another wire of the same material but twice the length and half the cross-sectional area, what is the new resistance?

Accepted Answer

$$R_{new} = 4R$$

Question 3

Which property of a material determines its resistance at a given temperature?

Accepted Answer

Resistivity $$\rho$$

Question 4

In a circuit, what is the role of an ideal electromotive force (emf) source?

Accepted Answer

It maintains a constant potential difference between its terminals.

Question 5

A battery with emf $$\mathcal{E}$$ and internal resistance $$r is $$connected to an external resistor $$R. $$What is the current in the circuit?

Accepted Answer

$$I = \frac{\mathcal{E}}{r + R}$$

Question 6

Three identical resistors are connected in series to a battery. What is true about the current through each resistor?

Accepted Answer

The current is the same in all three resistors.

Question 7

Three resistors $$R_1$$, $$R_2$$, and $$R_3$$ are connected in parallel across a battery. If $$R_1$$ \u003e $$R_2$$ \u003e $$R_3$$, which statement is true about the potential difference across each resistor?

Accepted Answer

$$V_1$$ = $$V_2$$ = $$V_3$$

Question 8

If the switch in a parallel circuit containing two identical resistors is opened, what happens to the reading on the voltmeter across one resistor?

Accepted Answer

It decreases.

Question 9

A light bulb is modeled as a resistor. If the current through the bulb increases, what happens to its brightness?

Accepted Answer

It gets brighter.

Question 10

In a parallel circuit, as more identical resistors are added, what happens to the total resistance between the two points?

Accepted Answer

It decreases.

Question 11

A circuit contains two resistors, $$R$$ and $$2R$$, connected in parallel across a battery. If the power output of the resistor $$R is$$ $$10\ \mathrm{W}$$, what is the power output of the resistor $$2R$$?

Accepted Answer

$$5\ \mathrm{W}$$

Question 12

Which of the following is Kirchhoff's junction rule?

Accepted Answer

The algebraic sum of the currents into a junction is zero: $$\sum I = 0.$$

Question 13

A circuit contains a resistor $$R$$ that produces heat at a rate of $$10\ \mathrm{W}. If it is $$replaced by a resistor of resistance $$2R in $$the same circuit, what is the power consumed?

Accepted Answer

$$5\ \mathrm{W}$$

Question 14

Three identical bulbs are connected in series to a battery. What is the correct ordering of their brightness?

Accepted Answer

All same brightness

Question 15

In a parallel circuit with three identical bulbs, how does the brightness of bulbs B and C change when the switch is closed?

Accepted Answer

B & C stay just as bright

Question 16

Consider two resistors in parallel, $$R_1 = 50$$\ \Omega$$ and R_2$ is a few milliOhms. Through which resistor does the largest current flow?

Accepted Answer

$$R_2$$

Question 17

Charge flows through a light bulb. Suppose a wire is connected across the bulb as shown. When the wire is connected, what happens?

Accepted Answer

All the charge flows through the wire.

Question 18

Given three light bulbs in a circuit, all with the same resistance $$R$$, and brightness proportional to power dissipated, the brightness of bulbs B and C together, compared with the brightness of bulb A, is:

Accepted Answer

Half as much

Question 19

Which of the following is Kirchhoff's loop rule?

Accepted Answer

The algebraic sum of the potential differences in any loop must equal zero: $$\sum V = 0.$$

Electric Circuits: Current, Resistance, Power, and Kirchhoff's Rules

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