Question 1

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 filed is the same everywhere 
C)  the electric field is strongest midway between Y and Z 
D)  Y is positive and Z is negative 
E)  Y and Z must have the same sign 
A)  Y is negative and Z is positive 
B)  the magnitude of the electric filed is the same everywhere 
C)  the electric field is strongest midway between Y and Z 
D)  Y is positive and Z is negative 
E)  Y and Z must have the same sign D

Question 2

The electric field due to a uniform distribution of charge on a spherical shell is zero:

Accepted Answer

A)  everywhere 
B)  nowhere 
C)  only at the center of the shell 
D)  only inside the shell 
E)  only outside the shell 
A)  everywhere 
B)  nowhere 
C)  only at the center of the shell 
D)  only inside the shell 
E)  only outside the shell D

Question 3

A spherical shell has an inner radius of 3.7 cm and an outer radius of 4.5 cm. If charge is distributed uniformly throughout the shell with a volume density of 6.1* 10-4 C/m3 the total charge is:

Accepted Answer

A)  1.0 * 10-7 C 
B)  1.3 * 10-7 C 
C)  2.0 *10-7 C 
D)  1.7 *10-6 C 
E)  5.0 * 10-6 C 
A)  1.0 * 10-7 C 
B)  1.3 * 10-7 C 
C)  2.0 *10-7 C 
D)  1.7 *10-6 C 
E)  5.0 * 10-6 C A

Question 4

An electric dipole consists of two charges, ±2.5 µC, separated by 1.0 x 10-4 m and centered on the origin. If the dipole is oriented along the x axis, what is the electric field at x = 15 cm?

Accepted Answer

A)  0 N/C 
B)  100 N/C 
C)  200 N/C 
D)  670 N/C 
E)  1300 N/C 
A)  0 N/C 
B)  100 N/C 
C)  200 N/C 
D)  670 N/C 
E)  1300 N/C

Question 5

Let k denote 1/4 $\pi$$\varepsilon$0. The magnitude of the electric field at a distance r from an isolated point charge q is:

Accepted Answer

A)  kq/r 
B)  kr/q 
C)  kq/r3 
D)  kq/r2 
E)  kq2/r2 
A)  kq/r 
B)  kr/q 
C)  kq/r3 
D)  kq/r2 
E)  kq2/r2

Question 6

A uniform electric field of 300 N/C makes an angle of 25$\degree$with the dipole moment of an electric dipole. If the torque exerted by the field has a magnitude of 2.5 *10-7 N.m, the dipole moment must be:

Accepted Answer

A)  8.3 *0 10-10 C.m 
B)  9.2 * 10-10 C.m 
C)  2.0 * 10-9 C.m 
D)  8.3 * 10-5 C.m 
E)  1.8 * 10-4 C.m 
A)  8.3 *0 10-10 C.m 
B)  9.2 * 10-10 C.m 
C)  2.0 * 10-9 C.m 
D)  8.3 * 10-5 C.m 
E)  1.8 * 10-4 C.m

Question 7

A 200-N/C electric field is in the positive x direction. The force on an electron in this field is:

Accepted Answer

A)  200 N in the positive x direction 
B)  200 N in the negative x direction 
C)  3.2 * 10-17 N, in the positive x direction 
D)  3.2 * 10-17 N, in the negative x direction 
E)  0 N 
A)  200 N in the positive x direction 
B)  200 N in the negative x direction 
C)  3.2 * 10-17 N, in the positive x direction 
D)  3.2 * 10-17 N, in the negative x direction 
E)  0 N

Question 8

Comparing the field of a single point charge with the field of an electric dipole,

Accepted Answer

A)  the field of the point charge decreases more rapidly with distance 
B)  the field of the point charge decreases less rapidly with distance 
C)  the field of the point charge decreases more rapidly with distance but only along the dipole axis 
D)  the field of the point charge decreases less rapidly with distance but only perpendicular to the dipole axis 
E)  the fields decrease equally rapidly with distance 
A)  the field of the point charge decreases more rapidly with distance 
B)  the field of the point charge decreases less rapidly with distance 
C)  the field of the point charge decreases more rapidly with distance but only along the dipole axis 
D)  the field of the point charge decreases less rapidly with distance but only perpendicular to the dipole axis 
E)  the fields decrease equally rapidly with distance

Question 9

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 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

An electric dipole of dipole moment 4.5 x 10-9 C·m is in a 250 N/C electric field. If the electric field points east, and the dipole moment vector points 37° west of south, what is the potential energy?

Accepted Answer

A)  -6.8 x 10-8 J 
B)  -9.0 x 10-7 J 
C)  0 J 
D)  6.8 x 10-8 J 
E)  9.0 x 10-7 J 
A)  -6.8 x 10-8 J 
B)  -9.0 x 10-7 J 
C)  0 J 
D)  6.8 x 10-8 J 
E)  9.0 x 10-7 J

Question 12

Two thin spherical shells, one with radius R and the other with radius 2R, surround an isolated charge point particle. The ratio of the number of field lines through the larger sphere to the number through the smaller is:

Accepted Answer

A)  1 
B)  2 
C)  4 
D)  1/2 
E)  1/4 
A)  1 
B)  2 
C)  4 
D)  1/2 
E)  1/4

Question 13

A disk with a uniform positive surface charge density lies in the x-y plane, centered on the origin. The disk contains 2.5 x 10-6 C/m2 of charge, and is 7.5 cm in radius. What is the electric field at z = 15 cm?

Accepted Answer

A)  30 N/C 
B)  300 N/C 
C)  3000 N/C 
D)  3.0 x 104 N/C 
E)  3.0 x 107 N/C 
A)  30 N/C 
B)  300 N/C 
C)  3000 N/C 
D)  3.0 x 104 N/C 
E)  3.0 x 107 N/C

Question 14

The diagram shows a particle with positive charge Q and a particle with negative charge-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 15

A charged oil drop with a mass of 2 *10-4 kg is held suspended by a downward electric field of 300 N/C. The charge on the drop is:

Accepted Answer

A)  +1.5 * 106 C 
B)  -1.5 * 106 C 
C)  +6.5 * 10-6 C 
D)  -6.5 *10-6 C 
E)  0 C 
A)  +1.5 * 106 C 
B)  -1.5 * 106 C 
C)  +6.5 * 10-6 C 
D)  -6.5 *10-6 C 
E)  0 C

Question 16

An electric field is most directly related to:

Accepted Answer

A)  the momentum of a test charge 
B)  the kinetic energy of a test charge 
C)  the potential energy of a test charge 
D)  the force acting on a test charge 
E)  the charge carried by a test charge 
A)  the momentum of a test charge 
B)  the kinetic energy of a test charge 
C)  the potential energy of a test charge 
D)  the force acting on a test charge 
E)  the charge carried by a test charge

Question 17

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)  7.4 * 10-11 C/m3  
B)  5.3 *10-5 C/m3 
C)  5.3 * 10-5 C/m2 
D)  8.5 *10-4 C/m3 
E)  5.0 * 10-3 C/m3 
A)  7.4 * 10-11 C/m3  
B)  5.3 *10-5 C/m3 
C)  5.3 * 10-5 C/m2 
D)  8.5 *10-4 C/m3 
E)  5.0 * 10-3 C/m3

Question 18

An electron traveling north enters a region where the electric field is uniform and points west. The electron:

Accepted Answer

A)  speeds up 
B)  slows down 
C)  veers east 
D)  veers west 
E)  continues with the same speed in the same direction 
A)  speeds up 
B)  slows down 
C)  veers east 
D)  veers west 
E)  continues with the same speed in the same direction

Question 19

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

Question 20

The torque exerted by an electric field on a dipole is:

Accepted Answer

A)  parallel to the field and perpendicular to the dipole moment 
B)  parallel to both the field and dipole moment 
C)  perpendicular to both the field and dipole moment 
D)  parallel to the dipole moment and perpendicular to the field 
E)  not related to the directions of the field and dipole moment 
A)  parallel to the field and perpendicular to the dipole moment 
B)  parallel to both the field and dipole moment 
C)  perpendicular to both the field and dipole moment 
D)  parallel to the dipole moment and perpendicular to the field 
E)  not related to the directions of the field and dipole moment

Exam 22: Electric Fields

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

The electric field due to a uniform distribution of charge on a spherical shell is zero:

A spherical shell has an inner radius of 3.7 cm and an outer radius of 4.5 cm. If charge is distributed uniformly throughout the shell with a volume density of 6.1* 10-4 C/m3 the total charge is:

An electric dipole consists of two charges, ±2.5 µC, separated by 1.0 x 10-4 m and centered on the origin. If the dipole is oriented along the x axis, what is the electric field at x = 15 cm?

Let k denote 1/4 π\piπε\varepsilonε 0. The magnitude of the electric field at a distance r from an isolated point charge q is:

A uniform electric field of 300 N/C makes an angle of 25 °\degree° with the dipole moment of an electric dipole. If the torque exerted by the field has a magnitude of 2.5 *10-7 N.m, the dipole moment must be:

A 200-N/C electric field is in the positive x direction. The force on an electron in this field is:

Comparing the field of a single point charge with the field of an electric dipole,

Electric field lines:

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:

An electric dipole of dipole moment 4.5 x 10-9 C·m is in a 250 N/C electric field. If the electric field points east, and the dipole moment vector points 37° west of south, what is the potential energy?

Two thin spherical shells, one with radius R and the other with radius 2R, surround an isolated charge point particle. The ratio of the number of field lines through the larger sphere to the number through the smaller is:

A disk with a uniform positive surface charge density lies in the x-y plane, centered on the origin. The disk contains 2.5 x 10-6 C/m2 of charge, and is 7.5 cm in radius. What is the electric field at z = 15 cm?

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

A charged oil drop with a mass of 2 *10-4 kg is held suspended by a downward electric field of 300 N/C. The charge on the drop is:

An electric field is most directly related to:

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:

An electron traveling north enters a region where the electric field is uniform and points west. The electron:

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.

The torque exerted by an electric field on a dipole is:

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A spherical shell has an inner radius of 3.7 cm and an outer radius of 4.5 cm. If charge is distributed uniformly throughout the shell with a volume density of 6.1* 10^-4 C/m³ the total charge is:

An electric dipole consists of two charges, ±2.5 µC, separated by 1.0 x 10^-4 m and centered on the origin. If the dipole is oriented along the x axis, what is the electric field at x = 15 cm?

Let k denote 1/4 $\pi$ $\varepsilon$ ₀. The magnitude of the electric field at a distance r from an isolated point charge q is:

A uniform electric field of 300 N/C makes an angle of 25 $\degree$ with the dipole moment of an electric dipole. If the torque exerted by the field has a magnitude of 2.5 *10^-7 N.m, the dipole moment must be:

An electric dipole of dipole moment 4.5 x 10^-9 C·m is in a 250 N/C electric field. If the electric field points east, and the dipole moment vector points 37° west of south, what is the potential energy?

A disk with a uniform positive surface charge density lies in the x-y plane, centered on the origin. The disk contains 2.5 x 10^-6 C/m² of charge, and is 7.5 cm in radius. What is the electric field at z = 15 cm?

A charged oil drop with a mass of 2 *10^-4 kg is held suspended by a downward electric field of 300 N/C. The charge on the drop 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: