Question 1

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 2

A physics instructor in an anteroom charges an electrostatic generator to 25 $\mu$C, then carries it into the lecture hall. The net electric flux in N . m2/C through the lecture hall walls is:

Accepted Answer

A)  0 
B)  25 *10-6 
C)  2.2 * 105 
D)  2.8 * 106 
E)  can't tell unless the lecture hall dimensions are given 
A)  0 
B)  25 *10-6 
C)  2.2 * 105 
D)  2.8 * 106 
E)  can't tell unless the lecture hall dimensions are given

Question 3

A 3.5-cm radius hemisphere contains a total charge of 6.6 * 10-7 C. The flux through the rounded portion of the surface is 9.8 * 104 N .m2/C. The flux through the flat base is:

Accepted Answer

A)  0 
B)  +2.3*104 N .m2/C 
C)  -2.3 * 104 N .m2/C 
D)  -9.8 *104 N .m2/C 
E)  +9.8* 104 N .m2/C 
A)  0 
B)  +2.3*104 N .m2/C 
C)  -2.3 * 104 N .m2/C 
D)  -9.8 *104 N .m2/C 
E)  +9.8* 104 N .m2/C

Question 4

A conducting sphere of radius 0.01 m has a charge of 1.0 * 10-9 C deposited on it. The magnitude of the electric field in N/C just outside the surface of the sphere is:

Accepted Answer

A)  zero 
B)  450 
C)  900 
D)  4500 
E)  90,000 
A)  zero 
B)  450 
C)  900 
D)  4500 
E)  90,000

Question 5

A point charge is placed at the center of a spherical Gaussian surface. The electric flux $\phi$E is changed if:

Accepted Answer

A)  the sphere is replaced by a cube of the same volume 
B)  the sphere is replaced by a cube of one-tenth the volume 
C)  the point charge is moved off center (but still inside the original sphere) 
D)  the point charge is moved to just outside the sphere 
E)  a second point charge is placed just outside the sphere 
A)  the sphere is replaced by a cube of the same volume 
B)  the sphere is replaced by a cube of one-tenth the volume 
C)  the point charge is moved off center (but still inside the original sphere) 
D)  the point charge is moved to just outside the sphere 
E)  a second point charge is placed just outside the sphere

Question 6

A round wastepaper basket with a 0.15-m radius opening is in a uniform electric field of 300 N/C, perpendicular to the opening. The total flux through the sides and bottom, in N . m2/C, is:

Accepted Answer

A)  0 
B)  4.2 
C)  21 
D)  280 
E)  can't tell without knowing the areas of the sides and bottom 
A)  0 
B)  4.2 
C)  21 
D)  280 
E)  can't tell without knowing the areas of the sides and bottom

Question 7

The table below gives the electric flux in N.m2/C through the ends and round surfaces of four gaussian surfaces in the form of cylinders. Rank the cylinders according to the charge inside, from the most negative to the most positive.

Accepted Answer

A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  3, 4, 2, 1 
D)  3, 1, 4, 2 
E)  4, 3, 1, 2 
A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  3, 4, 2, 1 
D)  3, 1, 4, 2 
E)  4, 3, 1, 2

Question 8

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 9

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)  can be a Gaussian surface since it is 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)  can be a Gaussian surface since it is an insulator 
D)  cannot be a Gaussian surface since it is an insulator 
E)  none of the above

Question 10

Charge Q is distributed uniformly throughout an insulating sphere of radius R. The magnitude of the electric field at a point R/2 from the center is:

Accepted Answer

A)  Q/4 $\pi$$\varepsilon$0R2 
B)  Q/ $\pi$$\varepsilon$0R2 
C)  3Q/4 $\pi$$\varepsilon$0R2 
D)  Q/8 $\pi$$\varepsilon$0R2 
E)  none of these 
A)  Q/4 $\pi$$\varepsilon$0R2 
B)  Q/ $\pi$$\varepsilon$0R2 
C)  3Q/4 $\pi$$\varepsilon$0R2 
D)  Q/8 $\pi$$\varepsilon$0R2 
E)  none of these

Question 11

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 12

Choose the INCORRECT statement:

Accepted Answer

A)  Gauss' law can be derived from Coulomb's law 
B)  Gauss' law states that the net number of lines crossing any closed surface in an outward direction is proportional to the net charge enclosed within the surface 
C)  Coulomb's law can be derived from Gauss' law and symmetry 
D)  Gauss' law applies to a closed surface of any shape 
E)  According to Gauss' law, if a closed surface encloses no charge, then the electric field must vanish everywhere on the surface 
A)  Gauss' law can be derived from Coulomb's law 
B)  Gauss' law states that the net number of lines crossing any closed surface in an outward direction is proportional to the net charge enclosed within the surface 
C)  Coulomb's law can be derived from Gauss' law and symmetry 
D)  Gauss' law applies to a closed surface of any shape 
E)  According to Gauss' law, if a closed surface encloses no charge, then the electric field must vanish everywhere on the surface

Question 13

A particle with charge Q is placed outside a large neutral conducting sheet. At any point in the interior of the sheet the electric field produced by charges on the surface is directed:

Accepted Answer

A)  toward the surface 
B)  away from the surface 
C)  toward Q 
D)  away from Q 
E)  none of the above 
A)  toward the surface 
B)  away from the surface 
C)  toward Q 
D)  away from Q 
E)  none of the above

Question 14

10 C of charge are placed on a spherical conducting shell. A particle with a charge of -3C is placed at the center of the cavity. The net charge in coulombs on the outer surface of the shell is:

Accepted Answer

A)  -7 
B)  -3 
C)  0 
D)  +3 
E)  +7 
A)  -7 
B)  -3 
C)  0 
D)  +3 
E)  +7

Exam 23: Gauss Law

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:

A physics instructor in an anteroom charges an electrostatic generator to 25 μ\muμ C, then carries it into the lecture hall. The net electric flux in N . m2/C through the lecture hall walls is:

A 3.5-cm radius hemisphere contains a total charge of 6.6 * 10-7 C. The flux through the rounded portion of the surface is 9.8 * 104 N .m2/C. The flux through the flat base is:

A conducting sphere of radius 0.01 m has a charge of 1.0 * 10-9 C deposited on it. The magnitude of the electric field in N/C just outside the surface of the sphere is:

A point charge is placed at the center of a spherical Gaussian surface. The electric flux ϕ\phiϕ E is changed if:

A round wastepaper basket with a 0.15-m radius opening is in a uniform electric field of 300 N/C, perpendicular to the opening. The total flux through the sides and bottom, in N . m2/C, is:

The table below gives the electric flux in N.m2/C through the ends and round surfaces of four gaussian surfaces in the form of cylinders. Rank the cylinders according to the charge inside, from the most negative to the most positive.

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:

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

Charge Q is distributed uniformly throughout an insulating sphere of radius R. The magnitude of the electric field at a point R/2 from the center 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:

Choose the INCORRECT statement:

A particle with charge Q is placed outside a large neutral conducting sheet. At any point in the interior of the sheet the electric field produced by charges on the surface is directed:

10 C of charge are placed on a spherical conducting shell. A particle with a charge of -3C is placed at the center of the cavity. The net charge in coulombs on the outer surface of the shell is:

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A physics instructor in an anteroom charges an electrostatic generator to 25 $\mu$ C, then carries it into the lecture hall. The net electric flux in N . m²/C through the lecture hall walls is:

A 3.5-cm radius hemisphere contains a total charge of 6.6 * 10^-⁷ C. The flux through the rounded portion of the surface is 9.8 * 10⁴ N .m²/C. The flux through the flat base is:

A conducting sphere of radius 0.01 m has a charge of 1.0 * 10^-⁹ C deposited on it. The magnitude of the electric field in N/C just outside the surface of the sphere is:

A point charge is placed at the center of a spherical Gaussian surface. The electric flux $\phi$ _E is changed if:

A round wastepaper basket with a 0.15-m radius opening is in a uniform electric field of 300 N/C, perpendicular to the opening. The total flux through the sides and bottom, in N . m²/C, is:

The table below gives the electric flux in N.m²/C through the ends and round surfaces of four gaussian surfaces in the form of cylinders. Rank the cylinders according to the charge inside, from the most negative to the most positive.

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: