Question 1

For a proton moving in the direction of the electric field

Accepted Answer

A)  its potential energy increases and its electric potential decreases. 
B)  its potential energy decreases and its electric potential increases. 
C)  its potential energy increases and its electric potential increases. 
D)  its potential energy decreases and its electric potential decreases. 
E)  both its potential energy and it electric potential remain constant.

Question 2

When a proton moves in a direction of the electric field, its potential increases but its potential energy decreases.

Accepted Answer

A) True 
 B)False

Question 3

A + 5.0-μC charge is moved from a negative to a positive plate of a parallel plate capacitor. In moving this charge 0.30 mJ of energy is used. What is the potential difference between the plates of this capacitor?

Accepted Answer

A)  60 V 
B)  81 V 
C)  55 V 
D)  23 V 
E)  0 V

Question 4

Every point on an equipotential surface is at the same potential.

Accepted Answer

A) True 
 B)False

Question 5

The capacitance of a parallel plate capacitor is directly proportional to its plate separation.

Accepted Answer

A) True 
 B)False

Question 6

When a dielectric material is introduced between the plates of a parallel plate capacitor the capacitance increases by a factor of 4. What is the dielectric constant of the material introduced between the plates?

Accepted Answer

A)  0.4 
B)  1/4 
C)  2 
D)  4 
E)  None of the other choices is correct.

Question 7

A parallel plate capacitor with plate separation of 4.0 cm has a plate area of 6.0 × 10-2 m2. What is the capacitance of this capacitor if a dielectric material with a dielectric constant of 2.4 is placed between the plates?

Accepted Answer

A)  3.7 × 10-12 F 
B)  3.7 × 10-14 F 
C)  16 × 10-14 F 
D)  32 × 10-14 F 
E)  32 × 10-12 F

Question 8

An equipotential surface must be

Accepted Answer

A)  parallel to the electric field at any point. 
B)  perpendicular to the electric field at any point. 
C)  randomly oriented with respect to the electric field. 
D)  equal to the electric field at any point.

Question 9

At a certain point in space the electric potential is 20 V. A 4.0-μC charge is brought from infinity to that point. What is the electric potential energy of this charge at that point?

Accepted Answer

A)  - 80 μJ 
B)  80 μJ 
C)  - 20 μJ 
D)  20 μJ 
E)  4.0 μJ

Question 10

FIGURE 20-13 
-The equipotential surfaces between the two point charges are shown in Figure 20-13 with the value of potential marked for each line. If the distance between points C and D is also 2.5 cm, what is the intensity of the electric field between these two points?

Accepted Answer

A)  2 V/m 
B)  4 V/m 
C)  6 V/m 
D)  8 V/m 
E)  10 V/m

Question 11

FIGURE 20-6 
-Four equal point charges of magnitude 6.00 μC and of varying signs are placed at the corners of a square 2.00 m on each side, as shown in Figure 20-6. What is the electric potential at the center of the square?

Accepted Answer

A)  0 V 
B)  76.4 kV 
C)  152.7 kV 
D)  61.0 kV 
E)  306 kV

Question 12

What charge appears on the plates of a 2.0-μF capacitor when it is charged to 100 V?

Accepted Answer

A)  0 μC 
B)  50 μC 
C)  100 μC 
D)  150 μC 
E)  200 μC

Question 13

A 4.0-μC charge is situated at the origin of an xy-coordinate system. What is the potential difference between a point x1 = 2.0 m and another point x2 = 5.0 m because of this charge?

Accepted Answer

A)  - 11 × 103 V 
B)  11 × 103 V 
C)  - 33 × 103 V 
D)  33 × 103 V 
E)  0 V

Question 14

At a certain point in space there is a potential of 400 V. What is the potential energy of a +2-μC charge at that point in space?

Accepted Answer

A)  80 × 10-6 J 
B)  800 J 
C)  400 J 
D)  200 J 
E)  8 × 10-4 J

Question 15

Which of the following will increase the capacitance of a parallel plate capacitor?

Accepted Answer

A)  a decrease in the plate area and an increase in the plate separation 
B)  a decrease in the potential difference between the plates 
C)  an increase in the potential difference between the plates 
D)  an increase in the plate area and a decrease in the plate separation 
E)  none of the above

Question 16

FIGURE 20-10 
-Two point charges of magnitude +4.00 μC and +2.00 μC are placed at the opposite corners of a rectangle as shown in Figure 20-10. What is the potential difference between points A and B?

Accepted Answer

A)  +203 × 103 V 
B)  -203 × 103 V 
C)  -22.5 × 103 V 
D)  +22.5 × 103 V 
E)  0 V

Question 17

A proton falls through a potential drop of 400 V. How much is the change of potential energy of this proton in falling through this potential drop?

Accepted Answer

A)  6.4 × 10-16 J 
B)  -6.4 × 10-16 J 
C)  17 × 10-16 J 
D)  -4000 J 
E)  4000 J

Question 18

A capacitor consists of a set of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery that maintains a constant potential difference between the plates. If the separation between the plates is doubled, the magnitude of the charge on the plates will

Accepted Answer

A)  double. 
B)  quadruple. 
C)  be cut in half. 
D)  be cut in fourth. 
E)  not change.

Question 19

Two point charges of magnitude 4.0 μC and -4.0 μC are situated along the x-axis at x1 = 2.0 m and x2 = -2.0 m, respectively. What is the electric potential energy of this system of charges?

Accepted Answer

A)  -36 mJ 
B)  36 mJ 
C)  0 J 
D)  -72 mJ 
E)  72 mJ

Exam 20: Electric Potential and Electric Potential Energy

For a proton moving in the direction of the electric field

When a proton moves in a direction of the electric field, its potential increases but its potential energy decreases.

A + 5.0-μC charge is moved from a negative to a positive plate of a parallel plate capacitor. In moving this charge 0.30 mJ of energy is used. What is the potential difference between the plates of this capacitor?

Every point on an equipotential surface is at the same potential.

The capacitance of a parallel plate capacitor is directly proportional to its plate separation.

When a dielectric material is introduced between the plates of a parallel plate capacitor the capacitance increases by a factor of 4. What is the dielectric constant of the material introduced between the plates?

A parallel plate capacitor with plate separation of 4.0 cm has a plate area of 6.0 × 10^-2 m². What is the capacitance of this capacitor if a dielectric material with a dielectric constant of 2.4 is placed between the plates?

An equipotential surface must be

At a certain point in space the electric potential is 20 V. A 4.0-μC charge is brought from infinity to that point. What is the electric potential energy of this charge at that point?

FIGURE 20-13 -The equipotential surfaces between the two point charges are shown in Figure 20-13 with the value of potential marked for each line. If the distance between points C and D is also 2.5 cm, what is the intensity of the electric field between these two points?

FIGURE 20-6 -Four equal point charges of magnitude 6.00 μC and of varying signs are placed at the corners of a square 2.00 m on each side, as shown in Figure 20-6. What is the electric potential at the center of the square?

What charge appears on the plates of a 2.0-μF capacitor when it is charged to 100 V?

A 4.0-μC charge is situated at the origin of an xy-coordinate system. What is the potential difference between a point x₁ = 2.0 m and another point x₂ = 5.0 m because of this charge?

At a certain point in space there is a potential of 400 V. What is the potential energy of a +2-μC charge at that point in space?

Which of the following will increase the capacitance of a parallel plate capacitor?

FIGURE 20-10 -Two point charges of magnitude +4.00 μC and +2.00 μC are placed at the opposite corners of a rectangle as shown in Figure 20-10. What is the potential difference between points A and B?

A proton falls through a potential drop of 400 V. How much is the change of potential energy of this proton in falling through this potential drop?

A capacitor consists of a set of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery that maintains a constant potential difference between the plates. If the separation between the plates is doubled, the magnitude of the charge on the plates will

Two point charges of magnitude 4.0 μC and -4.0 μC are situated along the x-axis at x₁ = 2.0 m and x₂ = -2.0 m, respectively. What is the electric potential energy of this system of charges?