Question 1

The outer surface of the cardboard center of a paper towel roll:

Accepted Answer

A)  is a possible Gaussian surface 
B)  cannot be a Gaussian surface because it encloses no charge 
C)  cannot be a Gaussian surface since it is not an insulator 
D)  cannot be a Gaussian surface since it is an insulator 
E)  none of the above 
A)  is a possible Gaussian surface 
B)  cannot be a Gaussian surface because it encloses no charge 
C)  cannot be a Gaussian surface since it is not an insulator 
D)  cannot be a Gaussian surface since it is an insulator 
E)  none of the above

Question 2

Charge Q is distributed uniformly throughout a spherical insulating shell. The net electric flux in N . m2/C through the inner surface of the shell is:

Accepted Answer

A)  0 
B)  Q/$\varepsilon$0 
C)  2Q/$\varepsilon$0 
D)  Q/4 $\pi$$\varepsilon$0 
E)  Q/2 $\pi$$\varepsilon$0 
A)  0 
B)  Q/$\varepsilon$0 
C)  2Q/$\varepsilon$0 
D)  Q/4 $\pi$$\varepsilon$0 
E)  Q/2 $\pi$$\varepsilon$0

Question 3

Which of the following graphs represents the magnitude of the electric field as a function of the distance from the center of a solid charged conducting sphere of radius R?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 4

A solid insulating sphere of radius R contains a positive charge that is distrubuted with a volume charge density that does not depend on angle but does increase with distance from the sphere center. Which of the graphs below correctly gives the magnitude E of the electric field as a function of the distance r from the center of the sphere?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 5

Charge is distributed uniformly along a long straight wire. The electric field 2 cm from the wire is 20 N/C. The electric field 4 cm from the wire is:

Accepted Answer

A)  120 N/C 
B)  80 N/C 
C)  40 N/C 
D)  10 N/C 
E)  5 N/C 
A)  120 N/C 
B)  80 N/C 
C)  40 N/C 
D)  10 N/C 
E)  5 N/C

Question 6

A hollow conductor is positively charged. A small uncharged metal ball is lowered by a silk thread through a small opening in the top of the conductor and allowed to touch its inner surface. After the ball is removed, it will have:

Accepted Answer

A)  a positive charge 
B)  a negative charge 
C)  no appreciable charge 
D)  a charge whose sign depends on what part of the inner surface it touched 
E)  a charge whose sign depends on where the small hole is located in the conductor 
A)  a positive charge 
B)  a negative charge 
C)  no appreciable charge 
D)  a charge whose sign depends on what part of the inner surface it touched 
E)  a charge whose sign depends on where the small hole is located in the conductor

Question 7

Two large insulating parallel plates carry charge of equal magnitude, one positive and the other negative, that is distributed uniformly over their inner surfaces. Rank the points 1 through 5 according to the magnitude of the electric field at the points, least to greatest.

Accepted Answer

A)  1, 2, 3, 4, 5 
B)  5, 4, 3, 2, 1 
C)  1, 4, and 5 tie, then 2 and 3 tie 
D)  2 and 3 tie, then 1 and 4 tie, then 5 
E)  2 and 3 tie, then 1, 4, and 5 tie 
A)  1, 2, 3, 4, 5 
B)  5, 4, 3, 2, 1 
C)  1, 4, and 5 tie, then 2 and 3 tie 
D)  2 and 3 tie, then 1 and 4 tie, then 5 
E)  2 and 3 tie, then 1, 4, and 5 tie

Question 8

A point particle with charge q is placed inside a cube but not at its center. The electric flux through any one side of the cube:

Accepted Answer

A)  is zero 
B)  is q/$\varepsilon$0 
C)  is q/4$\varepsilon$0 
D)  is q/6$\varepsilon$0 
E)  cannot be computed using Gauss' law 
A)  is zero 
B)  is q/$\varepsilon$0 
C)  is q/4$\varepsilon$0 
D)  is q/6$\varepsilon$0 
E)  cannot be computed using Gauss' law

Question 9

When a piece of paper is held with one face perpendicular to a uniform electric field the flux through it is 25 N . m2/C. When the paper is turned 25 $\degree$ with respect to the field the flux through it is:

Accepted Answer

A)  0 
B)  12 N .m2/C 
C)  21 N .m2/C 
D)  23 N . m2/C 
E)  25 N . m2/C 
A)  0 
B)  12 N .m2/C 
C)  21 N .m2/C 
D)  23 N . m2/C 
E)  25 N . m2/C

Question 10

Charge is distributed uniformly on the surface of a large flat plate. The electric field 2 cm from the plate is 30 N/C. The electric field 4 cm from the plate is:

Accepted Answer

A)  120 N/C 
B)  80 N/C 
C)  30 N/C 
D)  15 N/C 
E)  7.5 N/C 
A)  120 N/C 
B)  80 N/C 
C)  30 N/C 
D)  15 N/C 
E)  7.5 N/C

Question 11

Positive charge Q is placed on a conducting spherical shell with inner radius R1 and outer radius R2. A particle with charge q is placed at the center of the cavity. The magnitude of the electric field at a point in the cavity, a distance r from the center, is:

Accepted Answer

A)    
B)    
C)  q/4 $\pi$$\varepsilon$0r2 
D)  (q + Q)/4 $\pi$$\varepsilon$0r2 
E)    
A)    
B)    
C)  q/4 $\pi$$\varepsilon$0r2 
D)  (q + Q)/4 $\pi$$\varepsilon$0r2 
E)

Question 12

Consider Gauss law:   Which of the following is true?

Accepted Answer

A)    must be the electric field due to the enclosed charge 
B)  If q = 0 then   everywhere on the Gaussian surface 
C)  If the three particles inside have charges of +q, +q and -2q, then the integral is zero 
D)  On the surface   is everywhere parallel to   
E)  If a charge is placed outside the surface, then it cannot affect   on the at any point on the surface 
A)    must be the electric field due to the enclosed charge 
B)  If q = 0 then   everywhere on the Gaussian surface 
C)  If the three particles inside have charges of +q, +q and -2q, then the integral is zero 
D)  On the surface   is everywhere parallel to   
E)  If a charge is placed outside the surface, then it cannot affect   on the at any point on the surface

Question 13

A spherical conducting shell has charge Q. A particle with charge q is placed at the center of the cavity. The charge on the inner surface of the shell and the charge on the outer surface of the shell, respectively, are:

Accepted Answer

A)  0, Q 
B)  q, Q - q 
C)  Q, 0 
D)  -q, Q + q 
E)  -q, 0 
A)  0, Q 
B)  q, Q - q 
C)  Q, 0 
D)  -q, Q + q 
E)  -q, 0

Question 14

A particle with charge 5.0-$\mu$C is placed at the corner of a cube. The total electric flux in N.m2/C through all sides of the cube is:

Accepted Answer

A)  0 
B)  7.1 * 104 
C)  9.4 * 104 
D)  1.4 * 105 
E)  5.6 * 105 
A)  0 
B)  7.1 * 104 
C)  9.4 * 104 
D)  1.4 * 105 
E)  5.6 * 105

Exam 23: Gauss Law

The outer surface of the cardboard center of a paper towel roll:

Charge Q is distributed uniformly throughout a spherical insulating shell. The net electric flux in N . m2/C through the inner surface of the shell is:

Which of the following graphs represents the magnitude of the electric field as a function of the distance from the center of a solid charged conducting sphere of radius R?

Charge is distributed uniformly along a long straight wire. The electric field 2 cm from the wire is 20 N/C. The electric field 4 cm from the wire is:

A hollow conductor is positively charged. A small uncharged metal ball is lowered by a silk thread through a small opening in the top of the conductor and allowed to touch its inner surface. After the ball is removed, it will have:

Two large insulating parallel plates carry charge of equal magnitude, one positive and the other negative, that is distributed uniformly over their inner surfaces. Rank the points 1 through 5 according to the magnitude of the electric field at the points, least to greatest.

A point particle with charge q is placed inside a cube but not at its center. The electric flux through any one side of the cube:

When a piece of paper is held with one face perpendicular to a uniform electric field the flux through it is 25 N . m2/C. When the paper is turned 25 °\degree° with respect to the field the flux through it is:

Charge is distributed uniformly on the surface of a large flat plate. The electric field 2 cm from the plate is 30 N/C. The electric field 4 cm from the plate is:

Positive charge Q is placed on a conducting spherical shell with inner radius R1 and outer radius R2. A particle with charge q is placed at the center of the cavity. The magnitude of the electric field at a point in the cavity, a distance r from the center, is:

Consider Gauss law: Which of the following is true?

A spherical conducting shell has charge Q. A particle with charge q is placed at the center of the cavity. The charge on the inner surface of the shell and the charge on the outer surface of the shell, respectively, are:

A particle with charge 5.0- μ\muμ C is placed at the corner of a cube. The total electric flux in N.m2/C through all sides of the cube is:

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Charge Q is distributed uniformly throughout a spherical insulating shell. The net electric flux in N . m²/C through the inner surface of the shell is:

When a piece of paper is held with one face perpendicular to a uniform electric field the flux through it is 25 N . m²/C. When the paper is turned 25 $\degree$ with respect to the field the flux through it is:

Positive charge Q is placed on a conducting spherical shell with inner radius R₁ and outer radius R₂. A particle with charge q is placed at the center of the cavity. The magnitude of the electric field at a point in the cavity, a distance r from the center, is:

A particle with charge 5.0- $\mu$ C is placed at the corner of a cube. The total electric flux in N.m²/C through all sides of the cube is: