PHY101 MCQs Lectures 23-45

1. A total charge of 6.3 × 10−8 C is distributed uniformly throughout a 2.7-cm radius sphere. The volume charge density is: A.

3. 7 × 10−7 C/m3

B.

6. 9 × 10−6 C/m3

C.

6. 9 × 10−6 C/m2

D.

2. 5 × 10−4 C/m3

E.

7. 6 × 10−4 C/m3

Answer: E

2. Charge is placed on the surface of a 2.7-cm radius isolated conducting sphere. The surface charge density is uniform and has the value 6.9 × 10−6 C/m2. The total charge on the sphere is: A.

5. 6 × 10−10 C

B.

2. 1 × 10−8 C

C.

4. 7 × 10−8 C

D.

6. 3 × 10−8 C

E.

9. 5 × 10−3 C

Answer: D

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: A.

1. 0 × 10−7 C

B.

1. 3 × 10−7 C

C.

2. 0 × 10−7 C

D.

2. 3 × 10−7 C

E.

4. 0 × 10−7 C

Answer: A

4. 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: 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

Answer: D 5. 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◦ with respect to the field the flux through it is: A. B. 12 N · m2/C C. 21 N · m2/C D. 23 N · m2/C E. 25 N · m2/C

Answer: D

6. the yz plane is: A. 32 N · m2 /C B. 34 N · m2 /C C. 42 N · m2 /C D. 48 N · m2 /C E. 60 N · m2 /C

Answer: D

7. Consider Gauss’s law: nE · d nA = q/60. Which of the following is true?

A. nE must be the electric field due to the enclosed charge B. If q = 0, then nE = 0 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 nE is everywhere parallel to d nA E. If a charge is placed outside the surface, then it cannot affect nE at any point on the surface

Answer: C

8. A charged point particle is placed at the center of a spherical Gaussian surface. The electric flux ΦE is changed if: 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 offcenter (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

Answer: D

9. Choose the INCORRECT statement: 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

Answer: E 10. The outer surface of the cardboard center of a paper towel roll: 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 an insulator D. cannot be a Gaussian surface because it is not a closed surface E. none of the above

Answer: D

11. A physics instructor in an anteroom charges an electrostatic generator to 25 µC, then carries it into the lecture hall. The net electric flux in N · m2/C through the lecture hall walls is: A. B. 25 × 10−6 C.

2. 2 × 105

D.

2. 8 × 106

E. can not tell unless the lecture hall dimensions are given

Answer: D

12. A point particle with charge q is placed inside the cube but not at its center. The electric flux through any one side of the cube: A. is zero B. is q/60 C. is q/460 D. is q/660 E. cannot be computed using Gauss’ law

Answer: E

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

A. B.

7. 1 × 104

C.

9. 4 × 104

D.

1. 4 × 105

E.

5. 6 × 105

Answer: E

14. A point particle with charge q is at the center of a Gaussian surface in the form of a cube. The electric flux through any one face of the cube is: A. q/60 B. q/4π60 C. q/360 D. q/660 E. q/1260

Answer: D