Question 1

A copper 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 with length $$2L$$ and area $$A/2$$, what is the new resistance?

Accepted Answer

$$4R$$

Question 2

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

Accepted Answer

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

Question 3

Three identical resistors $$R$$ are connected in parallel. What is the total resistance $$R_{	ext{eq}} of $$the combination?

Accepted Answer

$$R_{	ext{eq}} = R/3$$

Question 4

A current of $$1.6\ 	ext{A}$$ flows through a wire. How many electrons pass through a cross-section of the wire every second? (Charge of electron $$e = 1.602 	imes 10$$^{-19}$$\ 	ext{C})$$

Accepted Answer

Question 5

Which statement about conventional current in a metallic conductor is correct?

Accepted Answer

It flows in the direction positive charges would move.

Question 6

A resistor dissipates power $$P = IV. If $$the resistor obeys Ohm's law, which of the following is also true?

Accepted Answer

$$P = V^2$/R$$

Question 7

Two resistors, $$R_1 = 4$$\ \Omega$$ and R_2$ = 6\ \Omega$$, are connected in series across a $$24\ 	ext{V}$$ battery. What is the current through the circuit?

Accepted Answer

$$2.0\ 	ext{A}$$

Question 8

A light bulb is rated at $$60\ 	ext{W}$$, $$120\ 	ext{V}. $$What is the resistance of the bulb when operating at rated voltage?

Accepted Answer

$$240\ \Omega$$

Question 9

If the cross-sectional area of a wire is doubled while keeping its length and material the same, what happens to its resistance?

Accepted Answer

It halves.

Question 10

A battery with emf $$2.5\ 	ext{V}$$ and internal resistance $$1\ \Omega$$ supplies a current of $$0.5\ 	ext{mA}. $$What is the terminal voltage?

Accepted Answer

$$2.0\ 	ext{V}$$

Question 11

Three resistors $$R_1$$, $$R_2$$, and $$R_3$$ are connected in parallel. If $$R_1$$ \u003e $$R_2$$ \u003e $$R_3$$, which resistor has the largest current?

Accepted Answer

$$R_3$$

Question 12

In a circuit, a switch is opened, increasing the total resistance. What happens to the current measured by an ammeter in the circuit?

Accepted Answer

It decreases.

Question 13

Which of the following is a correct application of Kirchhoff's junction rule?

Accepted Answer

The algebraic sum of currents entering a junction is zero.

Question 14

A circuit contains two resistors, $$R$$ and $$2R$$, in series with a battery. If the power output as heat from $$R is$$ $$P$$, what is the power output from $$2R$$?

Accepted Answer

$$P/2$$

Question 15

A voltmeter is connected across a resistor in a circuit. If the switch in the circuit is opened, what happens to the voltage reading?

Accepted Answer

It decreases.

Question 16

Which of the following best describes the drift velocity of electrons in a conductor with an applied electric field?

Accepted Answer

It is proportional to the electric field.

Question 17

A wire has resistance $$R at $$room temperature. If the temperature increases, what generally happens to the resistance?

Accepted Answer

It increases.

Question 18

In a parallel circuit, the potential difference across each resistor is:

Accepted Answer

The same for all resistors.

Question 19

A battery provides a constant emf but its internal resistance increases as it ages. What effect does this have on the terminal voltage when supplying current?

Accepted Answer

Terminal voltage decreases.

Question 20

Which of the following is true for three identical bulbs connected in parallel to a battery?

Accepted Answer

All bulbs have the same brightness.

Current, Resistance, and DC Circuits – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards