Question 1

A point charge of 3.0 µC is located on the y-axis at y = 4.0 m, and another point charge of 6.0 µC is located on the x-axis at x = 5.0 m. What is the direction (ccw from the x-axis) of the electric field at (5.0 m, 4.0 m)?

Accepted Answer

A)  72° 
B)  18° 
C)  25° 
D)  53° 
E)  34°

Question 2

A horizontally projected beam of electrons travels at 55 km/s into the space between two horizontal, parallel plates. The plates are separated by 7.4 cm, and they are 12 cm long. The uniform electric field between the plates is 7.2 mV/m upward. If the beam enters the region at a height of 3.7 cm above the lower plate, at what height above the lower plate does the beam exit the region? The electron mass is 9.11 × 10-31 kg.

Accepted Answer

A)  0.9 cm 
B)  2.3 cm 
C)  3.4 cm 
D)  4.6 cm

Question 3

A thin spherical shell of radius 20.0 cm has 5.0 µC of charge uniformly distributed over its surface. What is the electric flux through an area of 1.00 m2 of a spherical surface concentric with the shell of charge but having a radius of 1.00 m?

Accepted Answer

A)  5.6 × 105 N·m2/C 
B)  4.5 × 104 N·m2/C 
C)  1.8 × 104 N·m2/C 
D)  2.3 × 105 N·m2/C 
E)  0

Question 4

An electron is fired through the space between two oppositely charged, parallel plates. The plates form a 2.00 cm long region with an electric field of 4000 N/C perpendicular to the electron's initial velocity. If the initial speed of the electron is 1.00 × 107 m/s, what angle will its new velocity make relative to the direction of the original velocity?

Accepted Answer

A)  14° 
B)  8.0° 
C)  5.5° 
D)  4.6° 
E)  1.4°

Question 5

An electron gun sends electrons through a region with an electric field of magnitude 1.5 × 104 N/C for a distance of 2.5 cm. What is the acceleration of the electrons while in this electric field?

Accepted Answer

A)  1.4 × 108 m/s2 
B)  2.6 × 1011 m/s2 
C)  1.4 × 1012 m/s2 
D)  2.6 × 1015 m/s2 
E)  3.0 × 108 m/s2

Question 6

A conducting sphere of radius 10.0 cm holds a net charge of 4.4 µC. What is the surface charge density?

Accepted Answer

A)  0.0 
B)  3.5 × 10-5 C/m2 
C)  1.1 × 10-5 C/m2 
D)  2.2 × 10-4 C/m2 
E)  5.6 × 10-3 C/m2

Question 7

An electron is fired through the space between two oppositely charged, parallel plates. The plates form a 2.00 cm long region with an electric field of 4000 N/C perpendicular to the electron's initial velocity. If the initial speed of the electron is 1.00 × 107 m/s, how long does it take to traverse the plates?

Accepted Answer

A)  2.00 µs 
B)  2.00 ns 
C)  1.70 ns 
D)  1.80 ns 
E)  1.50 µs

Question 8

Each atom in a sample of lithium (Z = 3, atomic mass 6.941 u) has all of its electrons removed. If a charge of magnitude 1.0 mC was collected in this way, what is the mass of the lithium sample?

Accepted Answer

A)  0.010 µg 
B)  0.024 µg 
C)  0.031 µg 
D)  0.072 µg

Question 9

A hollow conducting spherical shell of radius 1.20 cm carries a charge of −5.20 nC. What is the electric field at a distance of 1.50 cm from the center of the shell?

Accepted Answer

A)  1.03 × 106 N/C outward 
B)  0 N/C 
C)  2.08 × 105 N/C inward 
D)  2.08 × 105 N/C outward 
E)  1.03 × 106 N/C inward

Question 10

Two charges are located on the x-axis. A 22 µC charge is located at the origin and a 47 µC charge is located at x = 4.0 m. What is the magnitude of the electric field at x = 7.5 m?

Accepted Answer

A)  4.0 × 105 N/C 
B)  3.8 × 104 N/C 
C)  5.7 × 105 N/C 
D)  6.3 × 104 N/C 
E)  2.5 × 106 N/C

Question 11

When the perpendicular distance from an infinitely long wire with a uniform linear charge distribution is tripled, what happens to the electric field strength?

Accepted Answer

A)  it stays the same 
B)  it decreases by a factor of 3 
C)  it decreases by a factor of 9 
D)  it decreases by a factor of (3)1/2 
E)  it increases by a factor of (3)1/2

Question 12

Each atom in a mole of water vapor (H2O) has one electron removed. What is the total charge of the ionized gas?

Accepted Answer

A)  96 kC 
B)  290 kC 
C)  600 kC 
D)  190 kC

Question 13

What is the total electric flux through a closed surface containing a 2.0 µC charge?

Accepted Answer

A)  1.8 × 104 N·m2/C 
B)  2.3 × 105 N·m2/C 
C)  1.4 × 105 N·m2/C 
D)  4.5 × 103 N·m2/C 
E)  0

Question 14

In a diagram of electric field lines, what is represented by lines that are drawn closer together?

Accepted Answer

A)  a more positive field 
B)  a more negative field 
C)  a stronger field 
D)  a weaker field 
E)  nothing (artistic license)

Question 15

Arrange the following from smallest to largest.

Accepted Answer

A)  mC, µC, nC, pC 
B)  µC, mC, pC, nC 
C)  nC, pC, mC, µC 
D)  pC, nC, µC, mC 
E)  nC, pC, µC, mC

Question 16

The electric field between two oppositely charged, parallel, conducting plates is

Accepted Answer

A)  zero. 
B)  strongest near the negative plate. 
C)  strongest near the positive plate. 
D)  approximately uniform.

Question 17

An imaginary spherical surface has radius 1.5 m. Fully contained within and concentric with the spherical surface is a spherical conductor with a uniform surface charge density of 1.5 × 10-7 C/m2. What is its radius if the flux through the imaginary surface is 480 Nm2/C?

Accepted Answer

A)  3.2 cm 
B)  4.7 cm 
C)  9.5 cm 
D)  6.4 cm 
E)  3.9 cm

Question 18

A 4.7 cm radius spherical conducting shell has a uniform surface charge density. What is the surface charge density if the electric field 1.5 m from its center is 17 N/C outward?

Accepted Answer

A)  1.5 × 10-7 C/m2 
B)  7.6 × 10-6 C/m2 
C)  1.1 × 10-7 C/m2 
D)  1.5 × 10-9 C/m2 
E)  6.1 × 10-7 C/m2

Question 19

Two alpha particles (helium nuclei) are separated by 4.0 × 10-15 m. What is the magnitude of the force between the particles due to their charge?

Accepted Answer

A)  6.8 × 10-22 N 
B)  4.5 × 10-19 N 
C)  1.1 × 10-4 N 
D)  14 N 
E)  58 N

Question 20

Two equal point charges are separated by a distance d. When the separation is reduced to d/4, what happens to the force between the charges?

Accepted Answer

A)  it decreases by a factor of 4 
B)  it increases by a factor of 4 
C)  it increases by a factor of 8 
D)  it increases by a factor of 16 
E)  it increases by a factor of more than 16

Exam 16: Electric Forces and Fields

A point charge of 3.0 µC is located on the y-axis at y = 4.0 m, and another point charge of 6.0 µC is located on the x-axis at x = 5.0 m. What is the direction (ccw from the x-axis) of the electric field at (5.0 m, 4.0 m) ?

A thin spherical shell of radius 20.0 cm has 5.0 µC of charge uniformly distributed over its surface. What is the electric flux through an area of 1.00 m² of a spherical surface concentric with the shell of charge but having a radius of 1.00 m?

An electron gun sends electrons through a region with an electric field of magnitude 1.5 × 10⁴ N/C for a distance of 2.5 cm. What is the acceleration of the electrons while in this electric field?