Question 1

The units of the electric field are:

Accepted Answer

A)  N . C2 
B)  C/N 
C)  N 
D)  N/C 
E)  C/m2 
A)  N . C2 
B)  C/N 
C)  N 
D)  N/C 
E)  C/m2 D

Question 2

Two point particles, one with charge +8 *10-9 C and the other with charge-2 * 10-9 C, are separated by 4 m. The electric field in N/C midway between them is:

Accepted Answer

A)  9 * 109 
B)  13,500 
C)  135,000 
D)  36 *10-9 
E)  22.5 
A)  9 * 109 
B)  13,500 
C)  135,000 
D)  36 *10-9 
E)  22.5 E

Question 3

Two protons (p1 and p2) are on the x axis, as shown below. The directions of the electric field at points 1, 2, and 3 respectively, are:

Accepted Answer

A)  $\rightarrow$, $\leftarrow$, $\rightarrow$ 
B)  $\leftarrow$, $\rightarrow$, $\leftarrow$ 
C)  $\leftarrow$, $\rightarrow$, $\rightarrow$ 
D)  $\leftarrow$, $\leftarrow$, $\leftarrow$ 
E)  $\leftarrow$, $\leftarrow$, $\rightarrow$ 
A)  $\rightarrow$, $\leftarrow$, $\rightarrow$ 
B)  $\leftarrow$, $\rightarrow$, $\leftarrow$ 
C)  $\leftarrow$, $\rightarrow$, $\rightarrow$ 
D)  $\leftarrow$, $\leftarrow$, $\leftarrow$ 
E)  $\leftarrow$, $\leftarrow$, $\rightarrow$ E

Question 4

The dipole moment of a dipole in a 300-N/C electric field is initially perpendicular to the field, but it rotates so it is in the same direction as the field. If the moment has a magnitude of 2 * 10-9 C . m the work done by the field is:

Accepted Answer

A)  -12 * 10-7 J 
B)  -6 *10-7 J 
C)  0 
D)  6 * 10-7 J 
E)  12 *10-7 J 
A)  -12 * 10-7 J 
B)  -6 *10-7 J 
C)  0 
D)  6 * 10-7 J 
E)  12 *10-7 J

Question 5

An electric field exerts a torque on a dipole only if:

Accepted Answer

A)  the field is parallel to the dipole moment 
B)  the field is not parallel to the dipole moment 
C)  the field is perpendicular to the dipole moment 
D)  the field is not perpendicular to the dipole moment 
E)  the field is uniform 
A)  the field is parallel to the dipole moment 
B)  the field is not parallel to the dipole moment 
C)  the field is perpendicular to the dipole moment 
D)  the field is not perpendicular to the dipole moment 
E)  the field is uniform

Question 6

Electric field lines:

Accepted Answer

A)  are trajectories of a test charge 
B)  are vectors in the direction of the electric field 
C)  form closed loops 
D)  cross each other in the region between two point charges 
E)  are none of the above 
A)  are trajectories of a test charge 
B)  are vectors in the direction of the electric field 
C)  form closed loops 
D)  cross each other in the region between two point charges 
E)  are none of the above

Question 7

The diagram shows a particle with positive charge Q and a particle with negative F-Q. The electric field at point P on the perpendicular bisector of the line joining them is:

Accepted Answer

A)  $\uparrow$ 
B)  $\downarrow$ 
C)  $\rightarrow$ 
D)  $\leftarrow$ 
E)  zero 
A)  $\uparrow$ 
B)  $\downarrow$ 
C)  $\rightarrow$ 
D)  $\leftarrow$ 
E)  zero

Question 8

The diagrams show four possible orientations of an electric dipole in a uniform electric field   Rank them according to the magnitude of the torque exerted on the dipole by the field, least to greatest.

Accepted Answer

A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  1, 2, 4, 3 
D)  3, 2 and 4 tie, then 1 
E)  1, 2 and 4 tie, then 3 
A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  1, 2, 4, 3 
D)  3, 2 and 4 tie, then 1 
E)  1, 2 and 4 tie, then 3

Question 9

The electric field at a distance of 10 cm from an isolated point particle with a charge of 2 *10-9 C is:

Accepted Answer

A)  1.8 N/C 
B)  180 N/C 
C)  18 N/C 
D)  1800 N/C 
E)  none of these 
A)  1.8 N/C 
B)  180 N/C 
C)  18 N/C 
D)  1800 N/C 
E)  none of these

Question 10

Two point particles, with the same charge, are located at two vertices of an equilateral triangle. A third charged particle is placed so the electric field at the third vertex is zero. The third particle must:

Accepted Answer

A)  be on the perpendicular bisector of the line joining the first two charges 
B)  be on the line joining the first two charges 
C)  be identical to the first two charges 
D)  have the same magnitude as the first two charges but may have a different sign 
E)  be at the center of the triangle 
A)  be on the perpendicular bisector of the line joining the first two charges 
B)  be on the line joining the first two charges 
C)  be identical to the first two charges 
D)  have the same magnitude as the first two charges but may have a different sign 
E)  be at the center of the triangle

Question 11

Positive charge Q is uniformly distributed on a semicircular rod. What is the direction of the electric field at point P, the center of the semicircle?

Accepted Answer

A)  $\uparrow$ 
B)  $\downarrow$ 
C) $\leftarrow$ 
D) $\rightarrow$ 
E)    
A)  $\uparrow$ 
B)  $\downarrow$ 
C) $\leftarrow$ 
D) $\rightarrow$ 
E)

Question 12

An electric dipole is oriented parallel to a uniform electric field, as shown.   It is rotated to one of the five orientations shown below. Rank the final orientations according to the change in the potential energy of the dipole-field system, most negative to most positive.

Accepted Answer

A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  1, 2, 4, 3 
D)  3, 2 and 4 tie, then 1 
E)  1, 2 and 4 tie, then 3 
A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  1, 2, 4, 3 
D)  3, 2 and 4 tie, then 1 
E)  1, 2 and 4 tie, then 3

Question 13

An isolated charged point particle produces an electric field with magnitude E at a point 2 m away. At a point 1 m from the particle the magnitude of the field is:

Accepted Answer

A)  E 
B)  2E 
C)  4E 
D)  E/2 
E)  E/4 
A)  E 
B)  2E 
C)  4E 
D)  E/2 
E)  E/4

Question 14

The diagram shows the electric field lines in a region of space containing two small charged spheres (Y and Z). Then:

Accepted Answer

A)  Y is negative and Z is positive 
B)  the magnitude of the electric field is the same everywhere 
C)  the electric field is strongest midway between Y and Z 
D)  the electric field is not zero anywhere (except infinitely far from the spheres) 
E)  Y and Z must have the same sign 
A)  Y is negative and Z is positive 
B)  the magnitude of the electric field is the same everywhere 
C)  the electric field is strongest midway between Y and Z 
D)  the electric field is not zero anywhere (except infinitely far from the spheres) 
E)  Y and Z must have the same sign

Question 15

Two charged point particle are located at two vertices of an equilateral triangle and the electric field is zero at the third vertex. We conclude:

Accepted Answer

A)  the two particles have charges with opposite signs and the same magnitude 
B)  the two particles have charges with opposite signs and different magnitudes 
C)  the two particles have identical charges 
D)  the two particles have charges with the same sign but different magnitudes 
E)  at least one other charged prticle is present 
A)  the two particles have charges with opposite signs and the same magnitude 
B)  the two particles have charges with opposite signs and different magnitudes 
C)  the two particles have identical charges 
D)  the two particles have charges with the same sign but different magnitudes 
E)  at least one other charged prticle is present

Question 16

The magnitude of the force of a 400-N/C electric field on a 0.02-C point charge is:

Accepted Answer

A)  8.0 N 
B)  8 *10-5 N 
C)  8 * 10-3 N 
D)  0.08 N 
E)  2 *1011 N 
A)  8.0 N 
B)  8 *10-5 N 
C)  8 * 10-3 N 
D)  0.08 N 
E)  2 *1011 N

Question 17

A charged particle is placed in an electric field that varies with location. No force is exerted on this charge:

Accepted Answer

A)  at locations where the electric field is zero 
B)  at locations where the electric field strength is 1/(1.6 * 10-19) N/C 
C)  if the particle is moving along a field line 
D)  if the particle is moving perpendicular to a field line 
E)  if the field is caused by an equal amount of positive and negative charge 
A)  at locations where the electric field is zero 
B)  at locations where the electric field strength is 1/(1.6 * 10-19) N/C 
C)  if the particle is moving along a field line 
D)  if the particle is moving perpendicular to a field line 
E)  if the field is caused by an equal amount of positive and negative charge

Question 18

An electric dipole consists of a particle with a charge of +6 * 10-6 C at the origin and a particle with a charge of -6 *10-6 C on the x axis at x = 3 * 10-3 m. Its dipole moment is:

Accepted Answer

A)  1.8 *10-8 C. m, in the positive x direction 
B)  1.8 * 10-8 C.m, in the negative x direction 
C)  0, because the net charge is 0 
D)  1.8 * 10-8 C . m, in the possitive y dirrection 
E)  1.8 * 10-8 C . m, in the negative y dirrection 
A)  1.8 *10-8 C. m, in the positive x direction 
B)  1.8 * 10-8 C.m, in the negative x direction 
C)  0, because the net charge is 0 
D)  1.8 * 10-8 C . m, in the possitive y dirrection 
E)  1.8 * 10-8 C . m, in the negative y dirrection

Question 19

A certain physics textbook shows a region of space in which two electric field lines cross each other. We conclude that:

Accepted Answer

A)  at least two point charges are present 
B)  an electrical conductor is present 
C)  an insulator is present 
D)  the field points in two directions at the same place 
E)  the author made a mistake 
A)  at least two point charges are present 
B)  an electrical conductor is present 
C)  an insulator is present 
D)  the field points in two directions at the same place 
E)  the author made a mistake

Question 20

A cylinder has a radius of 2.1 cm and a length of 8.8 cm. Total charge 6.1 * 10-7 C is distributed uniformly throughout. The volume charge density is:

Accepted Answer

A)  5.3 * 10-5 C/m3 
B)  5.3 *10-5 C/m2 
C)  8.5 * 10-4 C/m3 
D)  5.0 * 10-3 C/m3 
E)  6.3 * 10-2 C/m3 
A)  5.3 * 10-5 C/m3 
B)  5.3 *10-5 C/m2 
C)  8.5 * 10-4 C/m3 
D)  5.0 * 10-3 C/m3 
E)  6.3 * 10-2 C/m3

Exam 22: Electric Fields

The units of the electric field are:

Two point particles, one with charge +8 *10-9 C and the other with charge-2 * 10-9 C, are separated by 4 m. The electric field in N/C midway between them is:

Two protons (p1 and p2) are on the x axis, as shown below. The directions of the electric field at points 1, 2, and 3 respectively, are:

The dipole moment of a dipole in a 300-N/C electric field is initially perpendicular to the field, but it rotates so it is in the same direction as the field. If the moment has a magnitude of 2 * 10-9 C . m the work done by the field is:

An electric field exerts a torque on a dipole only if:

Electric field lines:

The diagram shows a particle with positive charge Q and a particle with negative F-Q. The electric field at point P on the perpendicular bisector of the line joining them is:

The diagrams show four possible orientations of an electric dipole in a uniform electric field Rank them according to the magnitude of the torque exerted on the dipole by the field, least to greatest.

The electric field at a distance of 10 cm from an isolated point particle with a charge of 2 *10-9 C is:

Two point particles, with the same charge, are located at two vertices of an equilateral triangle. A third charged particle is placed so the electric field at the third vertex is zero. The third particle must:

Positive charge Q is uniformly distributed on a semicircular rod. What is the direction of the electric field at point P, the center of the semicircle?

An electric dipole is oriented parallel to a uniform electric field, as shown. It is rotated to one of the five orientations shown below. Rank the final orientations according to the change in the potential energy of the dipole-field system, most negative to most positive.

An isolated charged point particle produces an electric field with magnitude E at a point 2 m away. At a point 1 m from the particle the magnitude of the field is:

The diagram shows the electric field lines in a region of space containing two small charged spheres (Y and Z). Then:

Two charged point particle are located at two vertices of an equilateral triangle and the electric field is zero at the third vertex. We conclude:

The magnitude of the force of a 400-N/C electric field on a 0.02-C point charge is:

A charged particle is placed in an electric field that varies with location. No force is exerted on this charge:

An electric dipole consists of a particle with a charge of +6 * 10-6 C at the origin and a particle with a charge of -6 *10-6 C on the x axis at x = 3 * 10-3 m. Its dipole moment is:

A certain physics textbook shows a region of space in which two electric field lines cross each other. We conclude that:

A cylinder has a radius of 2.1 cm and a length of 8.8 cm. Total charge 6.1 * 10-7 C is distributed uniformly throughout. The volume charge density is:

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Two point particles, one with charge +8 10^-⁹ C and the other with charge-2 10^-⁹ C, are separated by 4 m. The electric field in N/C midway between them is:

Two protons (p₁ and p₂) are on the x axis, as shown below. The directions of the electric field at points 1, 2, and 3 respectively, are:

The dipole moment of a dipole in a 300-N/C electric field is initially perpendicular to the field, but it rotates so it is in the same direction as the field. If the moment has a magnitude of 2 * 10^-⁹ C . m the work done by the field is:

The electric field at a distance of 10 cm from an isolated point particle with a charge of 2 *10^-⁹ C is:

An electric dipole consists of a particle with a charge of +6 * 10^-⁶ C at the origin and a particle with a charge of -6 10^-⁶ C on the x axis at x = 3 10^-³ m. Its dipole moment is:

A cylinder has a radius of 2.1 cm and a length of 8.8 cm. Total charge 6.1 * 10^-⁷ C is distributed uniformly throughout. The volume charge density is: