Chapter 28

Question 1

formula for potential energy is?

Answer 1

U=U(naught) +qEx

U(naught)=potential energy at the negative plate
x= distance from negative plate

Question 2

The electric potential inside a capacitor
A) is constant.
B) decreases inversely with distance from the negative plate.
C) increases linearly from the negative to the positive plate.
D) decreases linearly from the negative to the positive plate.
E) decreases inversely with the square of the distance from the negative plate.

Answer 2

C

Question 3

Refer to Figure Q28.3 on page 832. An electron moves along the trajectory from i to f. Which statement is true regarding the electron’s speed?
A) The speed decreases.
B) The speed increases.
C) The speed remains the same.

Answer 3

A

Question 4

A negative charge, if free, tries to move
A) from high potential to low potential.
B) away from infinity.
C) in the direction of the electric field.
D) toward infinity.
E) from low potential to high potential.

Answer 4

E

Question 5

An equipotential surface must be
A) equal to the electric field at every point.
B) oriented 30° with respect to the electric field at every point.
C) oriented 60° with respect to the electric field at every point.
D) perpendicular to the electric field at every point.
E) parallel to the electric field at every point.

Answer 5

D

Question 6

A positive and a negative charge are released from rest in vacuum. They move toward each other. As they do:(Hint: refer to Figure 28.9 on page 815)
A) A negative potential energy becomes less negative.
B) A positive potential energy becomes more positive.
C) A positive potential energy becomes less positive.
D) A negative potential energy becomes more negative.
E) A positive potential energy becomes a negative potential energy.

Answer 6

D

Question 7

When a proton moves in a direction of the electric field, its potential increases but its potential energy decreases.
A) True
B) False

Answer 7

B False

Question 8

A negative charge is moved from point A to point B along an equipotential surface. Which of the following statements is true for this case?
A) The negative charge performs work in moving from point A to point B.
B) Work is both required and performed in moving the negative charge from point A to point C) Not enough information is given to make a statement about the work involved.
D) Work is required to move the negative charge from point A to point B.
E) No work is required to move the negative charge from point A to point B.

Answer 8

E

Question 9

The potential outside a uniformly charged sphere is the same as if all the charge were concentrated at its center.
A) True
B) False

Answer 9

A True

Question 10

New units of the electric field were introduced in this chapter. What are they?
 A) V/C
 B) J/C
 C) J/m^2
 D) V/m
 E) N/C

Answer 10

D) V/m

Question 11

A capacitor with plates separated by distance d is charged to a potential difference ΔV. All wires and batteries are disconnected, then the two plates are pulled apart (with insulated handles) to a new separation of distance 2d. Choose the correct statement.
A) The potential difference decreases to ΔV/2.
B) The electric field between the plates increases by a factor of 2.
C) The electric field between the plates decreases by a factor of 2.
D) The charge on the capacitor plates decreases to one half of the original value.
E) The potential difference increases to 2ΔV.

Answer 11

E

Question 12

Equipotential lines and electric field lines
A) can cross at any angle.
B) never cross each other.
C) meet perpendicular to each other.

Answer 12

C