1. When a positive charge moves in the direction of the electric field,
Q23.1
When a positive charge moves in the direction of the electric field,
Motion
A. the field does positive work on it and the potential energy increases.
B. the field does positive work on it and the potential energy decreases.
C. the field does negative work on it and the potential energy increases.
D. the field does negative work on it and the potential energy decreases. +q
Answer: B

2. A23.1
When a positive charge moves in the direction of the electric field,
Motion
A. the field does positive work on it and the potential energy increases.
B. the field does positive work on it and the potential energy decreases.
C. the field does negative work on it and the potential energy increases.
D. the field does negative work on it and the potential energy decreases. +q

3. Q23.2
When a positive charge moves opposite to the direction of the electric field,
Motion +q
A. the field does positive work on it and the potential energy increases.
B. the field does positive work on it and the potential energy decreases.
C. the field does negative work on it and the potential energy increases.
D. the field does negative work on it and the potential energy decreases.
Answer: C

4. A23.2
When a positive charge moves opposite to the direction of the electric field,
Motion +q
A. the field does positive work on it and the potential energy increases.
B. the field does positive work on it and the potential energy decreases.
C. the field does negative work on it and the potential energy increases.
D. the field does negative work on it and the potential energy decreases.

5. When a negative charge moves in the direction of the electric field,
Q23.3
When a negative charge moves in the direction of the electric field,
Motion –q
A. the field does positive work on it and the potential energy increases.
B. the field does positive work on it and the potential energy decreases.
C. the field does negative work on it and the potential energy increases.
D. the field does negative work on it and the potential energy decreases.
Answer: C

6. A23.3
When a negative charge moves in the direction of the electric field,
Motion –q
A. the field does positive work on it and the potential energy increases.
B. the field does positive work on it and the potential energy decreases.
C. the field does negative work on it and the potential energy increases.
D. the field does negative work on it and the potential energy decreases.

7. Q23.4
When a negative charge moves opposite to the direction of the electric field,
Motion –q
A. the field does positive work on it and the potential energy increases.
B. the field does positive work on it and the potential energy decreases.
C. the field does negative work on it and the potential energy increases.
D. the field does negative work on it and the potential energy decreases.
Answer: B

8. A23.4
When a negative charge moves opposite to the direction of the electric field,
Motion –q
A. the field does positive work on it and the potential energy increases.
B. the field does positive work on it and the potential energy decreases.
C. the field does negative work on it and the potential energy increases.
D. the field does negative work on it and the potential energy decreases.

9. D. not enough information given to decide
Q23.5
The electric potential energy of two point charges approaches zero as the two point charges move farther away from each other.
If the three point charges shown here lie at the vertices of an equilateral triangle, the electric potential energy of the system of three charges is
Charge #2 +q
Charge #1 +q y –q x
Charge #3
positive.
B. negative.
C. zero.
D. not enough information given to decide
Answer: B

10. A23.5
The electric potential energy of two point charges approaches zero as the two point charges move farther away from each other.
If the three point charges shown here lie at the vertices of an equilateral triangle, the electric potential energy of the system of three charges is
Charge #2 +q
Charge #1 +q y –q x
Charge #3
positive.
B. negative.
C. zero.
D. not enough information given to decide

11. D. not enough information given to decide
Q23.6
The electric potential energy of two point charges approaches zero as the two point charges move farther away from each other.
If the three point charges shown here lie at the vertices of an equilateral triangle, the electric potential energy of the system of three charges is
Charge #2 –q
Charge #1 +q y –q x
Charge #3
positive.
B. negative.
C. zero.
D. not enough information given to decide
Answer: B

12. A23.6
The electric potential energy of two point charges approaches zero as the two point charges move farther away from each other.
If the three point charges shown here lie at the vertices of an equilateral triangle, the electric potential energy of the system of three charges is
Charge #2 –q
Charge #1 +q y –q x
Charge #3
positive.
B. negative.
C. zero.
D. not enough information given to decide

13. D. not enough information given to decide
Q23.7
The electric potential due to a point charge approaches zero as you move farther away from the charge.
If the three point charges shown here lie at the vertices of an equilateral triangle, the electric potential at the center of the triangle is
Charge #2 +q
Charge #1 +q y –q x
Charge #3
positive.
B. negative.
C. zero.
D. not enough information given to decide
Answer: A

14. A23.7
The electric potential due to a point charge approaches zero as you move farther away from the charge.
If the three point charges shown here lie at the vertices of an equilateral triangle, the electric potential at the center of the triangle is
Charge #2 +q
Charge #1 +q y –q x
Charge #3
positive.
B. negative.
C. zero.
D. not enough information given to decide

15. D. not enough information given to decide
Q23.8
The electric potential due to a point charge approaches zero as you move farther away from the charge.
If the three point charges shown here lie at the vertices of an equilateral triangle, the electric potential at the center of the triangle is
Charge #2 –q
Charge #1 +q y –q x
Charge #3
positive.
B. negative.
C. zero.
D. not enough information given to decide
Answer: B

16. A23.8
The electric potential due to a point charge approaches zero as you move farther away from the charge.
If the three point charges shown here lie at the vertices of an equilateral triangle, the electric potential at the center of the triangle is
Charge #2 –q
Charge #1 +q y –q x
Charge #3
positive.
B. negative.
C. zero.
D. not enough information given to decide

17. A. A point charge placed at P would feel no electric force.
Q23.9
Consider a point P in space where the electric potential is zero. Which statement is correct?
A. A point charge placed at P would feel no electric force.
B. The electric field at points around P is directed toward P.
C. The electric field at points around P is directed away from P.
D. none of the above
E. not enough information given to decide
Answer: E

18. A23.9
Consider a point P in space where the electric potential is zero. Which statement is correct?
A. A point charge placed at P would feel no electric force.
B. The electric field at points around P is directed toward P.
C. The electric field at points around P is directed away from P.
D. none of the above
E. not enough information given to decide

19. D. not enough information given to decide
Q23.10
Where an electric field line crosses an equipotential surface, the angle between the field line and the equipotential is
A. zero.
B. between zero and 90°.
C. 90°.
D. not enough information given to decide
Answer: C

20. A23.10
Where an electric field line crosses an equipotential surface, the angle between the field line and the equipotential is
A. zero.
B. between zero and 90°.
C. 90°.
D. not enough information given to decide

21. The direction of the electric potential gradient at a certain point
Q23.11
The direction of the electric potential gradient at a certain point
A. is the same as the direction of the electric field at that point.
B. is opposite to the direction of the electric field at that point.
C. is perpendicular to the direction of the electric field at that point.
D. not enough information given to decide
Answer: B

22. A23.11
The direction of the electric potential gradient at a certain point
A. is the same as the direction of the electric field at that point.
B. is opposite to the direction of the electric field at that point.
C. is perpendicular to the direction of the electric field at that point.
D. not enough information given to decide