AP PHYSICS C: ELECTRICITY AND MAGNETISM Scoring Guide
Unit 1 Progress Check: MCQ
Three identical point charges form an equilateral triangle with sides of length , as shown. The magnitude of the net
force acting on each point charge is , and the potential energy of the system of charges is . One of the three point
charges is then replaced by one with a charge .
1. If and , what is the magnitude of the net force on the point charge?
(A) Zero
(B)
(C)
(D)
(E)
2. Which of the following a correct expression for the potential energy of the system of three point charges in
?
(A)
(B)
(C)
(D)
(E) Zero
AP Physics C: Electricity and Magnetism Page 1 of 32
, Scoring Guide
Unit 1 Progress Check: MCQ
Two point charges with charges and are separated by distance . Several equipotential lines near the point
charges and labeled points , , , and are shown in the figure.
3. Which of the following correctly ranks the magnitudes of the electric field at the four labeled points from largest to
smallest?
(A)
(B)
(C)
(D)
(E)
Page 2 of 32 AP Physics C: Electricity and Magnetism
, Scoring Guide
Unit 1 Progress Check: MCQ
4.
A third point charges of charge is brought in from a large distance away and placed a distance from each of
the two original point charges, as shown above. Which of the following expressions is correct for the change of
electric potential energy from the two-point charges system to the three-point charges system?
(A) The electric potential energy is decreased by .
(B) The electric potential energy is decreased by .
(C) The electric potential energy is increased by .
(D) The electric potential energy is increased by .
(E) The electric potential energy is increased by .
5.
Two point charges are held at rest on the -axis of a coordinate system as shown above. The first point charge is
located at and has a charge of μ . The second point charge is located at
and has a charge of μ . Where must a third point charge with charge μ be placed so
that the net force on it is zero?
AP Physics C: Electricity and Magnetism Page 3 of 32
, Scoring Guide
Unit 1 Progress Check: MCQ
(A)
(B)
(C)
(D)
(E)
6.
Three point charges, each with charge of magnitude , are arranged in a line as shown. If the net force
on the middle charge is , what is the approximate value of ?
(A)
(B)
(C)
(D)
(E)
7. Point charges 1 and 2 have charges and and are held apart. The point charges exert an attractive
force of on each other. Which of the following are possible values for the charges?
(A) and
(B) and
(C) and
(D) and
(E) and
Page 4 of 32 AP Physics C: Electricity and Magnetism
Unit 1 Progress Check: MCQ
Three identical point charges form an equilateral triangle with sides of length , as shown. The magnitude of the net
force acting on each point charge is , and the potential energy of the system of charges is . One of the three point
charges is then replaced by one with a charge .
1. If and , what is the magnitude of the net force on the point charge?
(A) Zero
(B)
(C)
(D)
(E)
2. Which of the following a correct expression for the potential energy of the system of three point charges in
?
(A)
(B)
(C)
(D)
(E) Zero
AP Physics C: Electricity and Magnetism Page 1 of 32
, Scoring Guide
Unit 1 Progress Check: MCQ
Two point charges with charges and are separated by distance . Several equipotential lines near the point
charges and labeled points , , , and are shown in the figure.
3. Which of the following correctly ranks the magnitudes of the electric field at the four labeled points from largest to
smallest?
(A)
(B)
(C)
(D)
(E)
Page 2 of 32 AP Physics C: Electricity and Magnetism
, Scoring Guide
Unit 1 Progress Check: MCQ
4.
A third point charges of charge is brought in from a large distance away and placed a distance from each of
the two original point charges, as shown above. Which of the following expressions is correct for the change of
electric potential energy from the two-point charges system to the three-point charges system?
(A) The electric potential energy is decreased by .
(B) The electric potential energy is decreased by .
(C) The electric potential energy is increased by .
(D) The electric potential energy is increased by .
(E) The electric potential energy is increased by .
5.
Two point charges are held at rest on the -axis of a coordinate system as shown above. The first point charge is
located at and has a charge of μ . The second point charge is located at
and has a charge of μ . Where must a third point charge with charge μ be placed so
that the net force on it is zero?
AP Physics C: Electricity and Magnetism Page 3 of 32
, Scoring Guide
Unit 1 Progress Check: MCQ
(A)
(B)
(C)
(D)
(E)
6.
Three point charges, each with charge of magnitude , are arranged in a line as shown. If the net force
on the middle charge is , what is the approximate value of ?
(A)
(B)
(C)
(D)
(E)
7. Point charges 1 and 2 have charges and and are held apart. The point charges exert an attractive
force of on each other. Which of the following are possible values for the charges?
(A) and
(B) and
(C) and
(D) and
(E) and
Page 4 of 32 AP Physics C: Electricity and Magnetism
