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AP Physics C: Electricity and Magnetism Practice Quiz: Electrostatics with Conductors

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 11 questions to check your progress.

Question 1 of 11

A solid, isolated conducting sphere is given a net negative charge. Once the sphere reaches electrostatic equilibrium, where will the excess electrons be located?

All Questions (11)

A solid, isolated conducting sphere is given a net negative charge. Once the sphere reaches electrostatic equilibrium, where will the excess electrons be located?

A) Concentrated at the center of the sphere.

B) Uniformly distributed throughout the volume of the sphere.

C) Entirely on the outer surface of the sphere.

D) In a thin layer just beneath the surface.

Correct Answer: C

According to the provided content, in electrostatic equilibrium, the mutual repulsion of excess charge carriers forces them to reside entirely on the surface of the conductor.

What is the net electric field inside the material of a conductor that has reached electrostatic equilibrium?

A) Zero.

B) Uniform and non-zero.

C) Equal to the external electric field.

D) Directed towards the center of the conductor.

Correct Answer: A

The content states that when a conductor is in electrostatic equilibrium, the electric field is zero within the conductor. This is because all excess charges reside on the surface, resulting in no net charge in the interior.

A neutral, hollow conducting shell is placed in a uniform external electric field that points to the right. Which statement best describes the charge distribution on the shell?

A) The shell remains neutral everywhere with no charge separation.

B) Positive charge accumulates on the right surface and negative charge accumulates on the left surface.

C) Negative charge accumulates on the right surface and positive charge accumulates on the left surface.

D) Positive charge accumulates on both the left and right surfaces, while the top and bottom remain neutral.

Correct Answer: B

The conductor polarizes in the presence of an external electric field. The free charges inside the conductor move to maintain an equipotential surface, which cancels the external field inside. To cancel a field pointing right, negative charges move left (against the field) and positive charges are left on the right side.

The phenomenon where a closed conducting shell protects its interior from external electric fields is known as:

A) Electrostatic induction.

B) Conductor polarization.

C) Electrostatic shielding.

D) Equipotential separation.

Correct Answer: C

The provided text explicitly defines electrostatic shielding as the process of surrounding an area with a closed, conducting shell to create a region inside that is free from external electric fields.

A solid conductor in electrostatic equilibrium has a net charge of +Q. What is the net charge within any arbitrarily chosen volume completely inside the material of the conductor?

A) +Q

B) A fraction of +Q, depending on the size of the volume.

C) Zero.

D) -Q

Correct Answer: C

The content states that all excess charges reside on the surface of a conductor in electrostatic equilibrium. This means there is no net charge in the interior of the conductor. Therefore, any volume chosen entirely within the conductor will contain a net charge of zero.

What is the primary reason that excess charge carriers move to the surface of a conductor when it is in electrostatic equilibrium?

A) Attraction to charges outside the conductor.

B) The tendency to minimize electric potential.

C) Mutual repulsion between the like charges.

D) The insulating properties of the surrounding medium.

Correct Answer: C

The text specifies that 'mutual repulsion of excess charge carriers results in those charge carriers residing entirely on the surface of the conductor.' The like charges push each other as far apart as possible, which corresponds to the outer surface.

When a conductor is placed in an external electric field, it polarizes. This charge rearrangement occurs until the conductor becomes:

A) A perfect insulator.

B) Completely discharged.

C) An equipotential surface.

D) Magnetized.

Correct Answer: C

The provided content states that a conductor can be polarized in the presence of an external electric field and that this is a consequence of the conductor remaining an equipotential surface. The charges move until the potential is the same everywhere on the conductor.

A sensitive electronic device needs to be protected from stray external electric fields. Which of the following provides the most effective protection?

A) Placing the device in a thick glass box.

B) Surrounding the device with a plastic enclosure.

C) Grounding the device with a single wire.

D) Enclosing the device in a closed metal box.

Correct Answer: D

This is a direct application of electrostatic shielding. The content explains that surrounding an area with a closed, conducting shell (like a metal box) creates a region inside that is free from external electric fields.

Which of the following statements about a conductor in electrostatic equilibrium is FALSE?

A) The electric field within the conductor is zero.

B) Any excess charge resides on the surface of the conductor.

C) The net charge in the interior of the conductor is zero.

D) The electric potential is zero everywhere inside the conductor.

Correct Answer: D

While the electric field inside a conductor in equilibrium is zero, the electric potential is not necessarily zero. The conductor is an equipotential surface, meaning the potential is constant everywhere on and inside the conductor, but this constant value does not have to be zero.

A hollow, uncharged conducting sphere has a point charge +q placed at its exact center. After reaching electrostatic equilibrium, what is the electric field in the space between the inner surface of the sphere and the outer surface (i.e., within the conducting material itself)?

A) Zero.

B) Proportional to +q and directed radially outward.

C) Proportional to -q and directed radially inward.

D) Non-zero and uniform.

Correct Answer: A

Even with a charge inside its cavity, the electric field within the material of the conductor itself must be zero once it reaches electrostatic equilibrium. The charges within the conductor will rearrange (inducing -q on the inner surface and leaving +q on the outer surface) to ensure this condition is met.

The fact that the electric field is zero inside a conductor in electrostatic equilibrium is a direct consequence of:

A) The conductor having a net zero charge.

B) The free movement and redistribution of charge carriers.

C) The conductor being a perfect insulator.

D) The absence of any external electric fields.

Correct Answer: B

The electric field inside becomes zero because the free charge carriers (electrons) within the conductor move and redistribute themselves in response to any field until they create an internal field that perfectly cancels any field that would otherwise exist inside. This is possible because they are free to move.