Question 1

If more field lines leave a closed surface than enter that surface, then

Accepted Answer

A)  a net positive charge is contained inside the surface. 
B)  a net negative charge is contained inside the surface. 
C)  an error has been made since the number of field lines entering a surface must equal those leaving the surface. 
D)  an operating electron gun is inside the surface. 
E)  there must be a charge on the surface. 
A)  a net positive charge is contained inside the surface. 
B)  a net negative charge is contained inside the surface. 
C)  an error has been made since the number of field lines entering a surface must equal those leaving the surface. 
D)  an operating electron gun is inside the surface. 
E)  there must be a charge on the surface.

Question 2

Three point charges are positioned as follows: q1 is at (0.00 m, 0.00 m), q2 is at (1.20 m, 0.00 m), and q3 is at (1.20 m, 1.60 m). If all three charges are negative, into which quadrant is the force on q1 pointing?

Accepted Answer

A)  1st 
B)  2nd 
C)  3rd 
D)  4th 
E)  there isn't enough information in the problem to solve this 
A)  1st 
B)  2nd 
C)  3rd 
D)  4th 
E)  there isn't enough information in the problem to solve this

Question 3

In a diagram of electric field lines, q1 has 9 lines going into it and q2 has 27 lines going out of it. If one of the charges is −40 mC, which of the following could be the other one?

Accepted Answer

A)  −120 mC 
B)  18.0 mC 
C)  −18.0 mC 
D)  120 mC 
E)  none of these choices are correct 
A)  −120 mC 
B)  18.0 mC 
C)  −18.0 mC 
D)  120 mC 
E)  none of these choices are correct

Question 4

A thin spherical shell of radius 20.0 cm has 5.0 µC of charge uniformly distributed over its surface. What is the electric field 10.0 cm from the center of the sphere?

Accepted Answer

A)  4.5 × 106 N/C inward 
B)  4.5 × 106 N/C outward 
C)  2.3 × 106 N/C inward 
D)  2.3 × 106 N/C outward 
E)  0 
A)  4.5 × 106 N/C inward 
B)  4.5 × 106 N/C outward 
C)  2.3 × 106 N/C inward 
D)  2.3 × 106 N/C outward 
E)  0

Question 5

Three point charges are located on the x-axis. The first charge, q1 = 10.0 µC, is at x = −1.00 m; the second charge, q2 = 20.0 µC, is at the origin; and the third charge, q3 = −30.0 µC, is located at x = 2.00 m. What is the force on q3?

Accepted Answer

A)  1.65 N in the negative x-direction 
B)  3.15 N in the positive x-direction 
C)  1.50 N in the negative x-direction 
D)  4.80 N in the positive x-direction 
E)  4.65 N in the negative x-direction 
A)  1.65 N in the negative x-direction 
B)  3.15 N in the positive x-direction 
C)  1.50 N in the negative x-direction 
D)  4.80 N in the positive x-direction 
E)  4.65 N in the negative x-direction

Question 6

Three point charges are located on the x-axis. The first charge, q1 = 10.0 µC, is at x = −1.00 m; the second charge, q2 = 20.0 µC, is at the origin; and the third charge, q3 = −30.0 µC, is located at x = 2.00 m. Which charge is subjected to the force of greatest magnitude?

Accepted Answer

A)  q1 
B)  q2 
C)  q3 
D)  q1 and q2 (equal) 
E)  q2 and q3 (equal) 
A)  q1 
B)  q2 
C)  q3 
D)  q1 and q2 (equal) 
E)  q2 and q3 (equal)

Question 7

How many electrons does it take to make one coulomb of negative charge?

Accepted Answer

A)  1.00 × 109 
B)  6.24 × 1018 
C)  6.02 × 1023 
D)  1.66 × 1018 
E)  2.24 × 104 
A)  1.00 × 109 
B)  6.24 × 1018 
C)  6.02 × 1023 
D)  1.66 × 1018 
E)  2.24 × 104

Question 8

Three point charges are located on the x-axis. The first charge, q1 = 10.0 µC, is at x = −1.00 m; the second charge, q2 = 20.0 µC, is at the origin; and the third charge, q3 = −30.0 µC, is located at x = 2.00 m. What is the force on q2?

Accepted Answer

A)  1.65 N in the negative x-direction 
B)  3.15 N in the positive x-direction 
C)  1.50 N in the negative x-direction 
D)  4.80 N in the positive x-direction 
E)  4.65 N in the negative x-direction 
A)  1.65 N in the negative x-direction 
B)  3.15 N in the positive x-direction 
C)  1.50 N in the negative x-direction 
D)  4.80 N in the positive x-direction 
E)  4.65 N in the negative x-direction

Question 9

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 magnitude of the electric field at the position (5.0 m, 4.0 m)?

Accepted Answer

A)  2.7 × 103 N/C 
B)  3.5 × 103 N/C 
C)  2.7 × 10-3 N/C 
D)  3.5 × 10-3 N/C 
E)  4.5 × 103 N/C 
A)  2.7 × 103 N/C 
B)  3.5 × 103 N/C 
C)  2.7 × 10-3 N/C 
D)  3.5 × 10-3 N/C 
E)  4.5 × 103 N/C

Question 10

A spherical conducting shell has a uniform surface charge density of 1.5 × 10-7 C/m2. What is its radius if the electric field 1.5 m from its center is 17 N/C outward?

Accepted Answer

A)  3.9 cm 
B)  4.8 cm 
C)  3.2 cm 
D)  9.5 cm 
E)  6.4 cm 
A)  3.9 cm 
B)  4.8 cm 
C)  3.2 cm 
D)  9.5 cm 
E)  6.4 cm

Question 11

Each atom in a sample of lithium (Z=3, atomic mass 6.941u) has one electron 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)  0.024 µg 
B)  0.010 µg 
C)  0.031 µg 
D)  0.072 µg 
A)  0.024 µg 
B)  0.010 µg 
C)  0.031 µg 
D)  0.072 µg

Question 12

Four point charges are located at the corners of a square, 1.00 m by 1.00 m. On each of two diagonally opposite corners are 1.00 µC charges. On each of the other two corners are −1.00 µC charges. What is the direction of the force on each charge?

Accepted Answer

A)  positive charges away from away from the center of the square, negative inward toward the center 
B)  negative charges away from away from the center of the square, positive inward toward the center 
C)  positive and negative charges both toward the center of the square 
D)  positive and negative charges both away from the center of the square 
E)  no direction (net force on each charge = 0) 
A)  positive charges away from away from the center of the square, negative inward toward the center 
B)  negative charges away from away from the center of the square, positive inward toward the center 
C)  positive and negative charges both toward the center of the square 
D)  positive and negative charges both away from the center of the square 
E)  no direction (net force on each charge = 0)

Question 13

An arrangement of 3 charges is drawn showing the field lines. The first charge has 20 lines going into it. The second charge has 30 lines going out of it. If the net charge of the arrangement is zero, what is the field line situation for the third charge?

Accepted Answer

A)  50 lines going out 
B)  50 lines going in 
C)  10 lines going out 
D)  10 lines going in 
E)  600 lines going out to infinity 
A)  50 lines going out 
B)  50 lines going in 
C)  10 lines going out 
D)  10 lines going in 
E)  600 lines going out to infinity

Question 14

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 electric field at x = 3.00 m?

Accepted Answer

A)  4.5 × 105 N/C in the positive x-direction 
B)  4.9 × 105 N/C in the negative x-direction 
C)  4.0 × 105 N/C in the negative x-direction 
D)  4.9 × 105 N/C in the positive x-direction 
E)  6.3 × 105 N/C in the negative x-direction 
A)  4.5 × 105 N/C in the positive x-direction 
B)  4.9 × 105 N/C in the negative x-direction 
C)  4.0 × 105 N/C in the negative x-direction 
D)  4.9 × 105 N/C in the positive x-direction 
E)  6.3 × 105 N/C in the negative x-direction

Question 15

If a neutral metal object has been charged by friction to a charge of one pC, what has happened to it electrically?

Accepted Answer

A)  6.25 × 106 electrons have been added to it 
B)  6.25 × 106 protons have been added to it 
C)  6.25 × 106 electrons have been removed from it 
D)  6.25 × 106 protons have been removed from it 
E)  6.25 × 106 electrons and protons have been added to it 
A)  6.25 × 106 electrons have been added to it 
B)  6.25 × 106 protons have been added to it 
C)  6.25 × 106 electrons have been removed from it 
D)  6.25 × 106 protons have been removed from it 
E)  6.25 × 106 electrons and protons have been added to it

Question 16

An infinitely long wire with a uniform linear charge distribution has a charge per unit length of 2.3 × 10-6 C/m. What is the magnitude of the electric field at a perpendicular distance of 0.50 m from the wire?

Accepted Answer

A)  0.19 N/C 
B)  0.38 N/C 
C)  1.1 × 102 N/C 
D)  1.7 × 104 N/C 
E)  8.3 × 104 N/C 
A)  0.19 N/C 
B)  0.38 N/C 
C)  1.1 × 102 N/C 
D)  1.7 × 104 N/C 
E)  8.3 × 104 N/C

Question 17

A 72 nC charge is located at x = 3.00 m on the x-axis and an 8.0 nC charge is located at x = 7.0 m. At what point on the x-axis is the electric field zero?

Accepted Answer

A)  −9.0 m 
B)  4.0 m 
C)  −5.0 m 
D)  6.0 m 
E)  6.3 m 
A)  −9.0 m 
B)  4.0 m 
C)  −5.0 m 
D)  6.0 m 
E)  6.3 m

Question 18

When rubbing two insulators together, the one that gets a positive charge has had

Accepted Answer

A)  protons added. 
B)  protons removed. 
C)  electrons added. 
D)  electrons removed. 
E)  electrons added, and protons removed. 
A)  protons added. 
B)  protons removed. 
C)  electrons added. 
D)  electrons removed. 
E)  electrons added, and protons removed.

Question 19

The Coulomb constant k has a value of 8.99 × 109 N·m2/C2. The permittivity of vacuum εo has the units

Accepted Answer

A)  N·m2/C2. 
B)  N·m/C. 
C)  C/(N·m). 
D)  C2/(N·m2). 
E)  none of the choices are correct. 
A)  N·m2/C2. 
B)  N·m/C. 
C)  C/(N·m). 
D)  C2/(N·m2). 
E)  none of the choices are correct.

Question 20

Increasing the distance from a point charge by 34% changes the magnitude of the electric field by what amount?

Accepted Answer

A)  it decreases by 16% 
B)  it decreases by 34% 
C)  it decreases by 44% 
D)  it decreases by 80% 
E)  it stays the same 
A)  it decreases by 16% 
B)  it decreases by 34% 
C)  it decreases by 44% 
D)  it decreases by 80% 
E)  it stays the same

Exam 16: Electric Forces and Fields

If more field lines leave a closed surface than enter that surface, then

Three point charges are positioned as follows: q1 is at (0.00 m, 0.00 m), q2 is at (1.20 m, 0.00 m), and q3 is at (1.20 m, 1.60 m). If all three charges are negative, into which quadrant is the force on q1 pointing?

In a diagram of electric field lines, q1 has 9 lines going into it and q2 has 27 lines going out of it. If one of the charges is −40 mC, which of the following could be the other one?

A thin spherical shell of radius 20.0 cm has 5.0 µC of charge uniformly distributed over its surface. What is the electric field 10.0 cm from the center of the sphere?

Three point charges are located on the x-axis. The first charge, q1 = 10.0 µC, is at x = −1.00 m; the second charge, q2 = 20.0 µC, is at the origin; and the third charge, q3 = −30.0 µC, is located at x = 2.00 m. What is the force on q3?

Three point charges are located on the x-axis. The first charge, q1 = 10.0 µC, is at x = −1.00 m; the second charge, q2 = 20.0 µC, is at the origin; and the third charge, q3 = −30.0 µC, is located at x = 2.00 m. Which charge is subjected to the force of greatest magnitude?

How many electrons does it take to make one coulomb of negative charge?

Three point charges are located on the x-axis. The first charge, q1 = 10.0 µC, is at x = −1.00 m; the second charge, q2 = 20.0 µC, is at the origin; and the third charge, q3 = −30.0 µC, is located at x = 2.00 m. What is the force on q2?

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 magnitude of the electric field at the position (5.0 m, 4.0 m)?

A spherical conducting shell has a uniform surface charge density of 1.5 × 10-7 C/m2. What is its radius if the electric field 1.5 m from its center is 17 N/C outward?

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

Four point charges are located at the corners of a square, 1.00 m by 1.00 m. On each of two diagonally opposite corners are 1.00 µC charges. On each of the other two corners are −1.00 µC charges. What is the direction of the force on each charge?

An arrangement of 3 charges is drawn showing the field lines. The first charge has 20 lines going into it. The second charge has 30 lines going out of it. If the net charge of the arrangement is zero, what is the field line situation for the third charge?

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 electric field at x = 3.00 m?

If a neutral metal object has been charged by friction to a charge of one pC, what has happened to it electrically?

An infinitely long wire with a uniform linear charge distribution has a charge per unit length of 2.3 × 10-6 C/m. What is the magnitude of the electric field at a perpendicular distance of 0.50 m from the wire?

A 72 nC charge is located at x = 3.00 m on the x-axis and an 8.0 nC charge is located at x = 7.0 m. At what point on the x-axis is the electric field zero?

When rubbing two insulators together, the one that gets a positive charge has had

The Coulomb constant k has a value of 8.99 × 109 N·m2/C2. The permittivity of vacuum εo has the units

Increasing the distance from a point charge by 34% changes the magnitude of the electric field by what amount?

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Three point charges are positioned as follows: q₁ is at (0.00 m, 0.00 m), q₂ is at (1.20 m, 0.00 m), and q₃ is at (1.20 m, 1.60 m). If all three charges are negative, into which quadrant is the force on q₁ pointing?

In a diagram of electric field lines, q₁ has 9 lines going into it and q₂ has 27 lines going out of it. If one of the charges is −40 mC, which of the following could be the other one?

Three point charges are located on the x-axis. The first charge, q₁ = 10.0 µC, is at x = −1.00 m; the second charge, q₂ = 20.0 µC, is at the origin; and the third charge, q₃ = −30.0 µC, is located at x = 2.00 m. What is the force on q₃?

Three point charges are located on the x-axis. The first charge, q₁ = 10.0 µC, is at x = −1.00 m; the second charge, q₂ = 20.0 µC, is at the origin; and the third charge, q₃ = −30.0 µC, is located at x = 2.00 m. Which charge is subjected to the force of greatest magnitude?

Three point charges are located on the x-axis. The first charge, q₁ = 10.0 µC, is at x = −1.00 m; the second charge, q₂ = 20.0 µC, is at the origin; and the third charge, q₃ = −30.0 µC, is located at x = 2.00 m. What is the force on q₂?

A spherical conducting shell has a uniform surface charge density of 1.5 × 10^-7 C/m². What is its radius if the electric field 1.5 m from its center is 17 N/C outward?

An infinitely long wire with a uniform linear charge distribution has a charge per unit length of 2.3 × 10^-6 C/m. What is the magnitude of the electric field at a perpendicular distance of 0.50 m from the wire?

The Coulomb constant k has a value of 8.99 × 10⁹ N·m²/C². The permittivity of vacuum ε_o has the units