Question 1

A positive charge moves in the direction of a uniform electric field. Which statement is true about the work done by the electric field?

Accepted Answer

The electric field does positive work on the charge.

Question 2

Which equation correctly expresses the electric potential energy $U$ of a charge $q$ in a uniform electric field $E$ over a distance $x$?

Accepted Answer

$U = U_0 - qEx$

Question 3

A battery is connected across two large parallel plates separated by $d = 9.0\ \mathrm{mm}$, creating a potential difference of $V = 9.0\ \mathrm{V}$. An electron is released from the negative plate. What is its speed just before it hits the positive plate? (Electron mass $m = 9.11 	imes 10^{-31}\ \mathrm{kg}$, charge $e = 1.60 	imes 10^{-19}\ \mathrm{C}$)

Accepted Answer

$v = \sqrt{\dfrac{2eV}{m}}$

Question 4

The electric potential $V$ at a distance $r$ from a point charge $Q$ is given by which formula?

Accepted Answer

$V = \dfrac{kQ}{r}$

Question 5

Three point charges are arranged in a line: $2.0\ \mathrm{nC}$, $1.0\ \mathrm{nC}$, and $-3.0\ \mathrm{nC}$, each separated by $1.0\ \mathrm{m}$. What is the total potential energy stored in this configuration?

Accepted Answer

$U = -36\ \mathrm{nJ}$

Question 6

A charge $+q$ is placed at a distance $r$ from a charge $+Q$ (position A), and a charge $+2q$ is placed at a distance $2r$ from $+Q$ (position B). Compare the electric potential energy at A and B.

Accepted Answer

The potential energy at A is the same as at B.

Question 7

The voltage from a point charge $+Q$ at position A ($r$ away) and position B ($2r$ away) is:

Accepted Answer

Larger at A than at B.

Question 8

Which statement about equipotential lines and electric field lines is correct?

Accepted Answer

Electric field lines are always perpendicular to equipotential lines.

Question 9

A parallel-plate capacitor has plates of area $A$ separated by distance $d$. What is the formula for its capacitance $C$?

Accepted Answer

$C = \dfrac{\varepsilon_0 A}{d}$

Question 10

If the plates of a parallel-plate capacitor are moved closer together while the capacitor is disconnected from the battery, what happens to the capacitance?

Accepted Answer

The capacitance increases.

Question 11

Two capacitors, $C_1$ and $C_2$, are connected in series. What is the correct formula for the equivalent capacitance $C_{eq}$?

Accepted Answer

$C_{eq} = \dfrac{C_1 C_2}{C_1 + C_2}$

Question 12

Two capacitors, $C_1$ and $C_2$, are connected in parallel. What is the correct formula for the equivalent capacitance $C_{eq}$?

Accepted Answer

$C_{eq} = C_1 + C_2$

Question 13

A parallel-plate capacitor is charged to a potential $V$ and then disconnected from the battery. If the plates are pulled farther apart, what happens to the energy stored in the capacitor?

Accepted Answer

The energy increases.

Question 14

A dielectric material is inserted between the plates of a capacitor while the charge is held constant. What happens to the voltage across the plates?

Accepted Answer

The voltage decreases.

Question 15

The energy stored in a capacitor with charge $Q$ and capacitance $C$ is given by:

Accepted Answer

$U = \dfrac{1}{2} Q^2 / C$

Question 16

The energy density $u$ in the electric field between the plates of a parallel-plate capacitor is:

Accepted Answer

$u = \dfrac{1}{2} \varepsilon_0 E^2$

Question 17

A capacitor is connected to a battery and then disconnected. If a dielectric is inserted between the plates, what happens to the charge on the plates?

Accepted Answer

The charge stays the same.

Question 18

Which of the following statements about the electric field at the surface of a conductor is correct?

Accepted Answer

The electric field is perpendicular to the surface.

Question 19

If a charge $q$ is moved from a point at potential $V_1$ to a point at potential $V_2$, what is the work done by the electric field?

Accepted Answer

$W = -q(V_2 - V_1)$

Electric Potential and Capacitance: Structured Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards