1. They have the same potential energy. Both have zero potential energy.
Two rocks have equal mass. Which has more gravitational potential energy?
Rock A.
Rock B.
They have the same potential energy.
Both have zero potential energy.
Slide 28-25
B has more potential energy, it
Has been lifted up against
Gravity. 1 1

2. They have the same potential energy. Both have zero potential energy.
Two positive charges are equal. Which has more electric potential energy?
Charge A.
Charge B.
They have the same potential energy.
Both have zero potential energy.
A has the higher electric potential
Energy, one had to push it against
The electric field toward the positive
plate
Slide 28-28 2 2

3. They have the same potential energy. Both have zero potential energy.
Two negative charges are equal. Which has more electric potential energy?
Charge A.
Charge B.
They have the same potential energy.
Both have zero potential energy.
B has the higher electric potential
Energy, one had to move particle
Against E field towards negative
Plate. 3 3

4. They have the same potential energy. Both have zero potential energy.
A and B are an electron and proton respectively. Which has more electric potential energy?
The electron A.
The proton B.
They have the same potential energy.
Both have zero potential energy. C 4 4

5. They have the same potential energy. Both have zero potential energy.
A and B are two neutral hydrogen atoms. Which has more electric potential energy?
Atom A.
Atom B.
They have the same potential energy.
Both have zero potential energy. C 5 5

6. A positive potential energy becomes more positive.
A positive and a negative charge are released from rest in vacuum. They move toward each other. As they do:
A positive potential energy becomes more positive.
A positive potential energy becomes less positive.
A negative potential energy becomes more negative.
A negative potential energy becomes less negative.
A positive potential energy becomes a negative potential energy. C 6 6

7. the electric potential energy increases.
A positively charged object and a negatively charged object are pulled away from one another. Then:
the electric potential energy increases.
the electric potential energy stays the same.
the electric potential energy decreases.
A: the electric potential energy
Is KQ(-Q)/d is negative and
Moving the charges apart makes
The potential energy less negative and
So increases.

8. D. not enough information given to decide
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

9. D. not enough information given to decide
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

10. At the midpoint between these two equal but opposite charges,
E  0; V = 0.
E  0; V > 0.
E  0; V < 0.
E points right; V = 0.
E points left; V = 0. 10 10

11. At which point or points is the electric potential zero?B. C. D.
E. More than one of these. 11 11

12. A positive charge moves as shown. Its kinetic energy
Increases.
Remains constant.
Decreases.
C Decreases (moves to higher
Potential energy so loses
Kinetic energy)
Slide 28-35 12 12

13. Not enough information to compare the speeds at these points.
An electron follows the trajectory shown from point 1 to point 2. At point 2,
v2 > v1.
v2 = v1.
v2 < v1.
Not enough information to compare the speeds at these points.
C electron increases its potential
Energy as it moves further away
From attracting positive charge
So KE decreases. 13 13

14. Two protons, one after the other, are launched from point 1 with the same speed. They follow the two trajectories shown. The protons’ speeds at points 2 and 3 are related by
v2 > v3.
v2 = v3.
v2 < v3.
Not enough information to compare their speeds.
B: E field is conservative so change
In potential does not depend on
Path to equipotential surface. 14 14

15. Two conducting spheres, one charged other neutral15 15

16. A stronger electric field. A weaker electric field.
If a positive charge is released from rest, it moves in the direction of
A stronger electric field.
A weaker electric field.
Higher electric potential.
Lower electric potential.
Both B and D.
D lower electric potential 16 16

17. A proton is released from rest at the dot. Afterward, the proton
Remains at the dot.
Moves upward with steady speed.
Moves upward with an increasing speed.
Moves downward with a steady speed.
Moves downward with an increasing speed. 17 17

18. Slide 28-35 18 18

19. D. not enough information given to decide
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

20. A. A point charge placed at P would feel no electric force.
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

21. Metal spheres 1 and 2 are connected by a metal wire
Metal spheres 1 and 2 are connected by a metal wire. What quantities do spheres 1 and 2 have in common?
Same potential.
Same electric field.
Same charge.
Both A and B.
Both A and C.
A: same potential since these are all
Conductors connected to one another. 21 21

22. The smaller balloon empties into The bigger one.
Two identical balloons are connected after blowing one up to about ½ its maximum volume, the other to about ¼ its maximum volume. When the valve is turned so air can equalize between the two balloons
The balloons will become equal in size.
The large balloon will become a bit smaller, the
small balloon a bit bigger.
The large balloon will become bigger, the small
balloon smaller.
Nothing will happen.
The smaller balloon empties into
The bigger one.

23. At the midpoint between these two equal but opposite charges,
E  0; V = 0.
E  0; V > 0.
E  0; V < 0.
E points right; V = 0.
E points left; V = 0. D 23 23

24. Where is the electric potential zero?B. C. D.
E. More than one of these.
Answer is E, at points C and D 24 24

25. Multiply the vertical axis by -20 nC to get potential energy plot with vertical axis in multiples of 2 microjoules. The negative sign of the charge flips the graph upside down. (a) The point of maximum speed is then the point of lowest potential energy which occurs at x=8 cm
(b) particle's kinetic energy = 5 microjoule (add potential energy released to existing kinetic energy) (c) Turning point is when potential energy equals original kinetic energy, x=3 cm. (d) force on particle at turning point is charge times E=-dV/dx at x=3 so -20 nC times (0 -(-100)V)/( m) = ...

26. Estimate E along shortest path between two equipotential contours.

27. A particle follows the trajectory shown from initial position i to final position f. The potential difference V is
100 V.
50 V.
0 V.
50 V.
100 V.
Answer is D 27 27

28. A proton is released from rest at the dot. Afterward, the proton
Remains at the dot.
Moves upward with steady speed.
Moves upward with an increasing speed.
Moves downward with a steady speed.
Moves downward with an increasing speed.
Answer is E. 28 28

29. Which set of equipotential surfaces matches this electric field?
Answer is B 29 29

30. This is a graph of the x-component of the electric field along the x-axis. The potential is zero at the origin. What is the potential at x  1m?
2000 V.
1000 V.
0 V.
1000 V.
2000 V.
Answer is D 30 30

31. At which point is the electric field stronger? At xA. At xB.
The field is the same strength at both.
There’s not enough information to tell.
Answer is A 31 31

32. Move to the right ( x) at steady speed.
An electron is released from rest at x  2 m in the potential shown. What does the electron do right after being released?
Stay at x  2 m.
Move to the right ( x) at steady speed.
Move to the right with increasing speed.
Move to the left (x) at steady speed.
Move to the left with increasing speed.
Answer is D: negative slope of V gives
E field pointing to right, but electron
With negative charge moves in opposite
Direction. 32 32

33. The electric field at the dot is
10î V/m.
10î V/m.
20î V/m.
30î V/m.
30î V/m. 33 33

34. Not enough information to tell.
Metal wires are attached to the terminals of a 3 V battery. What is the potential difference between points 1 and 2?
6 V.
3 V.
0 V.
Undefined.
Not enough information to tell. B 34 34

35. What is the electric field magnitude E at point 5?
(a) 0 N/C
(b) N/C
(c) N/C
(d) N/C
(e) Not enough information C 35 35