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AP Physics 2 Unit 2: Electric Force, Field, and Potential

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Unit 2: Electric Force, Field, and Potential

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Question 1

A charge $q = + 2 μ C$ is moved from point A to point B in an electric field. The potential at A is $V_{A} = 100 V$ and at B is $V_{B} = 40 V$ . What is the work done by the electric field on the charge?

W = + 1.2 \times 1 0^{- 4} J

W = - 1.2 \times 1 0^{- 4} J

W = + 2.8 \times 1 0^{- 4} J

W = + 8.0 \times 1 0^{- 5} J

Question 2

Point P is located midway between two point charges: $+ 3 Q$ at $x = - d$ and $- Q$ at $x = + d$ . What is the direction of the net electric field at point P ( $x = 0$ )?

A.The field points in the

+ x

direction.B.The field points in the

- x

direction.C.The net field is zero because positive and negative charges cancel.D.The field points in the

+ y

direction.

Question 3

Two point charges $+ Q$ and $- Q$ are separated by distance $r$ . According to Coulomb's law, the magnitude of the electric force between them is:

F = \frac{k Q ^{2}}{r}

F = \frac{k Q ^{2}}{r ^{2}}

F = \frac{k Q}{r ^{2}}

F = \frac{2 k Q ^{2}}{r ^{2}}

Question 4

A parallel-plate capacitor has plate area $A$ and plate separation $d$ . If the separation is doubled while the charge on the plates remains constant, how does the voltage across the capacitor change?

A.The voltage is halved.B.The voltage is unchanged.C.The voltage doubles.D.The voltage quadruples.

Question 5

A dielectric material with dielectric constant $κ = 3$ is inserted between the plates of a parallel-plate capacitor connected to a battery (constant voltage). How does the energy stored in the capacitor change?

A.The stored energy decreases by a factor of 3.B.The stored energy increases by a factor of 3.C.The stored energy is unchanged because the voltage is constant.D.The stored energy increases by a factor of 9.

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Question 6

A positive test charge $+ q$ is placed in an electric field $E$ . The electric force on the test charge is:

F = E / q

F = q E

, directed opposite to

E

since the charge is positive.C.

F = q E

, directed in the same direction as

E

.D.

F = q^{2} E

Question 7

Two capacitors, $C_{1} = 4 μ F$ and $C_{2} = 12 μ F$ , are connected in series across a $24 V$ battery. What is the charge on $C_{1}$ ?

Q_{1} = 96 μ C

Q_{1} = 288 μ C

Q_{1} = 72 μ C

Q_{1} = 18 μ C

Question 8

Equipotential surfaces around a positive point charge are:

A.Parallel planes perpendicular to the radial electric field lines.B.Concentric spheres centered on the charge.C.Lines radiating outward from the charge.D.Ellipsoidal surfaces elongated along the direction of the field.

Question 9

An electron (charge $- e$ ) is released from rest at a point where the electric potential is $V = - 50 V$ and moves to a point where $V = + 50 V$ . By how much does the electron's kinetic energy increase?

Δ K E = - 1.6 \times 1 0^{- 17} J

(electron loses energy)B.

Δ K E = + 8.0 \times 1 0^{- 18} J

Δ K E = + 1.6 \times 1 0^{- 17} J

Δ K E = 0

(electron starts from rest so gains no energy)

Question 10

An electron is fired horizontally into a uniform electric field directed vertically downward with magnitude $E = 500 N/C$ . The electron has initial speed $v_{0} = 2.0 \times 1 0^{6} m/s$ . What is the magnitude of the electron's acceleration? ( $m_{e} = 9.11 \times 1 0^{- 31} kg$ , $e = 1.6 \times 1 0^{- 19} C$ )

a \approx 8.8 \times 1 0^{13} m/ s^{2}

a \approx 4.4 \times 1 0^{13} m/ s^{2}

a \approx 8.8 \times 1 0^{10} m/ s^{2}

a \approx 5.5 \times 1 0^{14} m/ s^{2}

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Question 11

Three point charges are placed along a line: $+ Q$ at $x = 0$ , $- Q$ at $x = d$ , and $+ Q$ at $x = 2 d$ . At the point $x = d$ (the location of the $- Q$ charge), the net electric field due to the other two charges points in which direction?

A.In the

+ x

directionB.In the

- x

directionC.The net electric field at

x = d

from the two

+ Q

charges is zero.D.Perpendicular to the line (in the

y

-direction)

Question 12

A parallel-plate capacitor with plate separation $d$ is connected to a battery maintaining voltage $V_{0}$ . A conducting slab of thickness $d /2$ is inserted between the plates (not touching either plate). How does the capacitance change?

A.The capacitance is unchanged.B.The capacitance doubles.C.The capacitance is halved.D.The capacitance increases by a factor of 4.

AP Physics 2 Unit 2: Electric Force, Field, and Potential — Free with Answer Explanations | Test Practice Hub