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AP Physics C: Electricity and Magnetism Practice Quiz: Electric Charge and Electric Force

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

Test your understanding with short quizzes. This quiz has 16 questions to check your progress.

Question 1 of 16

According to the provided content, which of the following describes the electric force between two objects with like charges (e.g., both positive)?

All Questions (16)

According to the provided content, which of the following describes the electric force between two objects with like charges (e.g., both positive)?

A) A repulsive force

B) An attractive force

C) A gravitational force

D) No force

Correct Answer: A

The content states that electric force results from the interactions between charged objects. The fundamental rule of these interactions is that like charges repel each other.

Two point charges are separated by a distance *r* and exert an electrostatic force of magnitude *F* on each other. If the distance between the charges is doubled to *2r*, what will be the new magnitude of the electrostatic force?

A) 4F

B) 2F

C) F/2

D) F/4

Correct Answer: D

According to Coulomb's Law, the electric force is inversely proportional to the square of the distance between the charges (F ∝ 1/r²). If the distance *r* is doubled (multiplied by 2), the force will be multiplied by 1/(2²), which is 1/4. The new force will be F/4.

In the context of analyzing electric forces, what is the primary characteristic of a 'point charge' model?

A) It has no mass.

B) Its physical size is considered negligible.

C) It can only be positively charged.

D) It does not exert a gravitational force.

Correct Answer: B

The provided text defines a point charge as a model where 'the physical size of a charged object or system is negligible in the context of the situation being analyzed.'

For any two objects that possess both mass and electric charge, how does the magnitude of the gravitational force typically compare to the magnitude of the electrostatic force between them?

A) The gravitational force is usually much larger.

B) The electrostatic force is usually much smaller.

C) The two forces are always equal in magnitude.

D) The electrostatic force is usually much larger.

Correct Answer: D

The content explicitly states that 'For any two objects that have mass and electric charge, the magnitude of the gravitational force is usually much smaller than the magnitude of the electrostatic force.'

What does the electric permittivity of a material measure?

A) The total charge a material can hold.

B) The strength of the gravitational field within the material.

C) The degree to which the material is polarized by an electric field.

D) The speed at which charge moves through the material.

Correct Answer: C

The provided content defines electric permittivity as 'a measurement of the degree to which a material or medium is polarized in the presence of an electric field.'

Two point charges, q₁ and q₂, exert an electrostatic force of magnitude *F* on each other. If the magnitude of q₁ is doubled and the magnitude of q₂ is tripled, what is the new magnitude of the force?

A) 5F

B) 6F

C) F/6

D) F/5

Correct Answer: B

Coulomb's Law states that the force is directly proportional to the product of the two charges (F ∝ |q₁q₂|). If q₁ is multiplied by 2 and q₂ is multiplied by 3, the product |q₁q₂| is multiplied by 2 * 3 = 6. Therefore, the new force will be 6F.

According to the provided text, what is described as a fundamental property of all matter?

A) Permittivity

B) Mass

C) Charge

D) Polarization

Correct Answer: C

The text begins by stating, 'Charge is a fundamental property of all matter.'

The electrostatic force between two point charges is *F*. If the magnitude of one charge is doubled and the distance between the charges is halved, what is the new force?

A) F

B) 2F

C) 4F

D) 8F

Correct Answer: D

The force is proportional to the charge (F ∝ q) and inversely proportional to the square of the distance (F ∝ 1/r²). Doubling one charge multiplies the force by 2. Halving the distance (multiplying by 1/2) multiplies the force by 1/((1/2)²), which is 1/(1/4) or 4. The combined effect is 2 * 4 = 8. The new force is 8F.

Which law describes the electrostatic force between two charged objects?

A) The Law of Universal Gravitation

B) The Law of Permittivity

C) The Law of Point Charges

D) Coulomb's Law

Correct Answer: D

The provided content explicitly states that 'Coulomb's law describes the electrostatic force between two charged objects.'

The electrostatic force between two charges is *F*. To change the force to *F*/16, the distance between the charges must be multiplied by what factor?

A) 1/16

B) 1/4

C) 4

D) 16

Correct Answer: C

Force is inversely proportional to the square of the distance (F ∝ 1/r²). To get a force of F/16, we need 1/r² to become 1/16 of its original value. This means r² must be 16 times larger. Taking the square root, the distance *r* must be multiplied by a factor of 4.

For two objects to exert both an electric force and a gravitational force on each other, they must both have which two properties?

A) Charge and permittivity

B) Mass and charge

C) Mass and volume

D) Charge and size

Correct Answer: B

The content describes the forces that result from interactions between charged objects with mass. Gravitational force requires mass, and electric force requires charge.

According to Coulomb's Law, $|\vec{F}_{E}|=k rac{|q_{1}q_{2}|}{r^{2}}$, the magnitude of the electrostatic force is inversely proportional to which quantity?

A) The product of the charges, |q₁q₂|

B) The distance between the charges, r

C) The square of the distance between the charges, r²

D) The electrostatic constant, k

Correct Answer: C

In the equation for Coulomb's Law, the term for distance, r, is in the denominator and is squared. This indicates an inverse square relationship, meaning the force is inversely proportional to the square of the distance, r².

Two point charges exert a force *F* on each other. If the magnitude of one charge is quadrupled (multiplied by 4) and the distance between them is doubled (multiplied by 2), what is the new force?

A) F/2

B) F

C) 2F

D) 8F

Correct Answer: B

The force is proportional to the charge (F ∝ q) and inversely proportional to the square of the distance (F ∝ 1/r²). Quadrupling one charge multiplies the force by 4. Doubling the distance multiplies the force by 1/(2²), which is 1/4. The combined effect is 4 * (1/4) = 1. The new force is 1*F, or F.

The interaction that results in an attractive or repulsive force between two charged objects is known as the:

A) Gravitational force

B) Permittivity force

C) Electric force

D) Point charge force

Correct Answer: C

The first point of the provided content explicitly describes the 'electric force that results from the interactions between charged objects or systems.'

An object with a positive charge is brought near an object with a negative charge. The resulting electric force would be described as:

A) Repulsive

B) Attractive

C) Negligible

D) Gravitational

Correct Answer: B

The principles of electric force state that opposite charges attract. Since one object is positive and the other is negative, the force between them will be attractive.

If the magnitude of the electrostatic force between two fixed point charges increases, which of the following could be a possible cause according to Coulomb's Law?

A) The distance between the charges was increased.

B) The magnitude of one of the charges was decreased.

C) The charges were moved into a medium with a higher electric permittivity.

D) The distance between the charges was decreased.

Correct Answer: D

According to Coulomb's Law, F is proportional to |q₁q₂| and inversely proportional to r². An increase in force could be caused by an increase in the magnitude of the charges or a decrease in the distance. Of the options provided, only decreasing the distance (r) would result in an increased force.