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AP Physics C: Electricity and Magnetism Easy practice

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Question 1

A solenoid of $N = 500$ turns, length $ℓ = 0.25 m$ , and cross-sectional area $A = 2.0 \times 1 0^{- 4} m^{2}$ carries current $I$ . The self-inductance of the solenoid is:

L = μ_{0} n^{2} A ℓ \approx 0.20 mH

L = μ_{0} N A / ℓ \approx 0.50 μ H

L = μ_{0} N^{2} / (A ℓ) \approx 1.26 \times 1 0^{9} H

L = μ_{0} N^{2} A \approx 6.28 \times 1 0^{- 5} H

Question 2

Two point charges $q_{1} = + 3 μ C$ and $q_{2} = - 3 μ C$ are separated by $r = 0.30 m$ . Using $k = 9 \times 1 0^{9} N\cdotm^{2} / C^{2}$ , the magnitude of the electric force between them is:

0.90 N

0.30 N

0.10 N

8.1 \times 1 0^{- 3} N

Question 3

Lenz's law states that the direction of the induced current in a loop is such that:

A.The induced current's magnetic field opposes the change in flux that caused it.B.The induced current's magnetic field reinforces the change in flux, amplifying the effect.C.The induced current always flows clockwise when viewed from above.D.The induced EMF is proportional to the magnetic flux, not its rate of change.

Question 4

A solid insulating sphere of radius $R$ carries uniform volume charge density $ρ$ . For a point inside the sphere at radius $r < R$ , Gauss's law gives the electric field magnitude:

E = \frac{ρ R ^{3}}{3 ϵ _{0} r ^{2}}

E = \frac{ρ r}{3 ϵ _{0}}

E = \frac{ρR}{3 ϵ _{0}}

E = 0

Question 5

An infinitely long line charge has linear charge density $λ > 0$ . Using Gauss's law with a coaxial cylindrical Gaussian surface of radius $r$ and length $L$ , the electric field at distance $r$ from the line is:

E = \frac{λ}{2 π ϵ _{0} r ^{2}}

E = \frac{λ}{2 π ϵ _{0} r}

E = \frac{λ L}{2 π ϵ _{0} r}

E = \frac{λ}{4 π ϵ _{0} r}

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Question 6

A uniformly charged thin ring of radius $R$ and total charge $Q$ lies in the $x y$ -plane centered at the origin. The electric field on the axis of the ring at distance $z$ from the center points:

A.Radially outward from the ring's center, perpendicular to the axis.B.Along the

z

-axis (axial direction) for

z \neq = 0

.C.In the plane of the ring, toward the nearest point of the ring.D.Zero everywhere on the axis.

Question 7

An ammeter has negligible resistance. A voltmeter has very high resistance. Which connection correctly measures the voltage across resistor $R_{2}$ in a series circuit containing $R_{1}$ and $R_{2}$ ?

A.Connect the voltmeter in parallel with

R_{2}

and the ammeter in series in the branch containing

R_{2}

.B.Connect both the voltmeter and ammeter in series with

R_{2}

.C.Connect the voltmeter in series with

R_{2}

and the ammeter in parallel with

R_{2}

.D.Connect both the voltmeter and ammeter in parallel with

R_{2}

Question 8

A parallel-plate capacitor has plate area $A$ and plate separation $d$ . The capacitance is:

C = \frac{ϵ _{0} A}{d}

C = \frac{ϵ _{0} d}{A}

C = \frac{A}{4 π ϵ _{0} d}

C = \frac{ϵ _{0} A}{2 d}

Question 9

A long straight wire carries current $I = 5 A$ . The magnetic field at a perpendicular distance $r = 0.10 m$ from the wire has magnitude (using $μ_{0} = 4 π \times 1 0^{- 7} T\cdotm/A$ ):

B = 10 μ T

B = 100 μ T

B = 1 μ T

B = 50 μ T

Question 10

A spherical capacitor consists of an inner shell of radius $a$ and a concentric outer shell of radius $b$ ( $b > a$ ). The capacitance of this spherical capacitor is:

C = 4 π ϵ_{0} ab / (b - a)

C = 4 π ϵ_{0} (b - a) / (ab)

C = 4 π ϵ_{0} a

C = ϵ_{0} \cdot 4 π a^{2} / (b - a)

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Question 11

A proton ( $q = + e$ , $m_{p}$ ) moves with velocity $v = v \overset{x}{^}$ through a magnetic field $B = B \overset{z}{^}$ . The magnetic force on the proton is:

F = - e v B \overset{y}{^}

, directed in the

- y

direction.B.

F = + e v B \overset{y}{^}

, directed in the

+ y

direction.C.

F = + e v B \overset{z}{^}

, directed along the magnetic field.D.

F = 0

, because the proton moves perpendicular to the field.

Question 12

A resistor $R = 10 Ω$ is connected to a battery of EMF $E = 20 V$ and internal resistance $r = 2 Ω$ . The current through the circuit is:

I = 2 A

I = 5/3 A \approx 1.67 A

I = 10 A

I = 1 A

Question 13

A conductor in electrostatic equilibrium has which of the following properties?

A.The electric field just outside the surface is

σ / ϵ_{0}

, directed perpendicular to the surface.B.The electric field inside the conductor is

σ / ϵ_{0}

.C.The electric potential varies parabolically throughout the conductor's volume.D.Excess charge distributes uniformly throughout the conductor's volume.

Question 14

A solenoid of length $L = 0.50 m$ , $N = 1000$ turns, and radius $r ≪ L$ carries current $I = 2 A$ . Using Ampère's law, the magnetic field inside the solenoid is:

B = μ_{0} n I \approx 5.0 mT

B = μ_{0} N I / (2 π r)

B = μ_{0} N I / L^{2}

B = μ_{0} I / (2 π r)

Question 15

A coaxial cylindrical capacitor has inner radius $a$ , outer radius $b$ , and length $L$ . The capacitance per unit length is:

C / L = \frac{2 π ϵ _{0}}{ln ( b / a )}

C / L = \frac{π ϵ _{0}}{ln ( b / a )}

C / L = \frac{2 π ϵ _{0} ( b - a )}{ab ln ( b / a )}

C / L = \frac{2 π ϵ _{0}}{b - a}

AP Physics C: Electricity and Magnetism Easy practice — Free with Answer Explanations | Test Practice Hub