AP Physics Physics: Electricity & Magnetism 2

Question 1

A parallel-plate capacitor is fully charged and then disconnected from the battery. If the plate separation is doubled, what happens to the voltage across the capacitor?

Accepted Answer

It doubles

Answer

With the battery disconnected, charge Q is constant; since C = ε₀A/d and V = Q/C, doubling d halves C and therefore doubles V.

Question 2

Two long parallel wires carry currents in the same direction. The magnetic force between them is:

Accepted Answer

Attractive

Answer

Parallel currents in the same direction create magnetic fields that cause the wires to attract each other.

Question 3

A proton moves horizontally to the right through a uniform magnetic field directed into the page. The magnetic force on the proton is directed:

Accepted Answer

Upward

Answer

Using F = qv × B with v to the right (+x) and B into the page (−z), the cross product gives force in the +y (upward) direction.

Question 4

Which of the following correctly describes the electric field inside a conductor in electrostatic equilibrium?

Accepted Answer

It is zero

Answer

In electrostatic equilibrium, free charges redistribute until the net electric field inside the conductor is exactly zero.

Question 5

A solenoid with N turns, length L, and cross-sectional area A carries current I. Its self-inductance is:

Accepted Answer

μ₀N²A/L

Answer

The self-inductance of a solenoid is L = μ₀N²A/ℓ, derived from the flux linkage NΦ = N·(μ₀NI/ℓ)·A.

AP Practice Test

AP Practice Test

AP Physics Physics: Electricity & Magnetism 2