Question 1

Which of the following best describes electric potential energy?

Accepted Answer

The energy stored in the interaction between a charged particle and an electric field.

Question 2

A proton is released from rest at the midpoint between the plates of a parallel-plate capacitor with a potential difference of $V = 100\ \mathrm{V}$. What is the change in electric potential energy as the proton moves to the negative plate?

Accepted Answer

$\Delta U = -eV$

Question 3

The electric potential energy of two point charges $q_1$ and $q_2$ separated by a distance $r$ is given by:

Accepted Answer

$U = \dfrac{1}{4\pi\varepsilon_0} \dfrac{q_1 q_2}{r}$

Question 4

A water molecule with dipole moment $p$ is aligned with an electric field $E$. How much energy is required to rotate the molecule by $90^\circ$?

Accepted Answer

$\Delta U = pE$

Question 5

Which statement about equipotential surfaces is correct?

Accepted Answer

Equipotential surfaces are always perpendicular to the electric field.

Question 6

A parallel-plate capacitor has a capacitance $C = 1.0\ \mathrm{pF}$ and is charged to $V = 1.5\ \mathrm{V}$. What is the charge stored on the plates?

Accepted Answer

$Q = CV = 1.5\ \mathrm{pC}$

Question 7

A proton is fired from far away at a glass sphere of diameter $1.0\ \mathrm{mm}$ charged to $+100\ \mathrm{nC}$. What initial kinetic energy must the proton have to just reach the surface?

Accepted Answer

$K = \dfrac{1}{4\pi\varepsilon_0} \dfrac{qQ}{r}$

Question 8

Which of the following is true for capacitors connected in series?

Accepted Answer

They all have the same charge.

Question 9

The energy stored in a capacitor of capacitance $C$ charged to voltage $V$ is:

Accepted Answer

$U = \dfrac{1}{2}CV^2$

Question 10

A parallel-plate capacitor is filled with a dielectric of constant $\kappa$. How does the capacitance change compared to the empty capacitor?

Accepted Answer

It increases by a factor of $\kappa$.

Question 11

A conducting sphere of radius $r$ is charged to potential $V$. What is the charge on the sphere?

Accepted Answer

$Q = 4\pi\varepsilon_0 r V$

Question 12

The relationship between electric field $E$ and electric potential $V$ in one dimension is:

Accepted Answer

$E = -\dfrac{dV}{dx}$

Question 13

A capacitor is constructed using a dielectric with $\kappa = 3.00$ and dielectric strength $2.0 	imes 10^7\ \mathrm{V/m}$. If the desired capacitance is $0.250\ \mathrm{pF}$ and the maximum potential difference is $4,000\ \mathrm{V}$, what is the minimum area required for the plates?

Accepted Answer

$A = \dfrac{Cd}{\kappa\varepsilon_0}$

Question 14

Which of the following statements about conductors in electrostatic equilibrium is correct?

Accepted Answer

The electric field inside the conductor is zero.

Question 15

A thin conducting spherical shell of radius $R$ carries a total charge $Q$. What is the electric potential at a point outside the shell at distance $r$ from the center ($r > R$)?

Accepted Answer

$V = \dfrac{1}{4\pi\varepsilon_0} \dfrac{Q}{r}$

Question 16

A uniformly charged ring of radius $a$ and total charge $Q$ produces an electric potential at a point on its axis at distance $x$ from the center. Which expression gives the potential at that point?

Accepted Answer

$V = \dfrac{1}{4\pi\varepsilon_0} \dfrac{Q}{\sqrt{x^2 + a^2}}$

Question 17

If the electric field between the plates of a parallel-plate capacitor is $E$ and the plate separation is $d$, what is the potential difference between the plates?

Accepted Answer

$V = Ed$

Question 18

A Geiger counter consists of a cylindrical tube of radius $R$ and a wire of radius $r$ along its axis. The capacitance per unit length of the system is:

Accepted Answer

$C' = \dfrac{2\pi\varepsilon_0}{\ln(R/r)}$

Question 19

A capacitor with capacitance $C$ is charged to voltage $V$ and then disconnected from the battery. If a dielectric with constant $\kappa$ is inserted, what happens to the voltage across the plates?

Accepted Answer

The voltage decreases by a factor of $\kappa$.

Electric Potential, Potential Energy, and Electric Field: Study Notes for Physics

Study Guide - Practice Questions

Study Guide - Flashcards