PHY101 Final Term Past Paper 2

PHY101

Q14. 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:

1. q/0
2. q/4π0
3. q/30
4. q/60

Correct answer: q/60

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. Left end right end rounded surface

cylinder 1: +2 × 10−9 +4 × 10−9 −6 × 10−9 · cylinder 2: +3 × 10−9 −2 × 10−9 +6 × 10−9 · cylinder 3: −2 × 10−9 −5 × 10−9 +3 × 10−9

cylinder 4: +2 × 10−9 −5 × 10−9 −3 × 10−9

1. 1, 2, 3, 4
2. 4, 3, 2, 1
3. 3, 4, 2, 1
4. 4, 3, 1, 2

Correct answer: 4, 3, 1, 2

A conducting sphere of radius 0.01m 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:

1. 0

PHY101

1. 450
2. 900
3. 4500

Correct answer: 900

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

1. 0
2. 4.2
3. 21
4. 280

Correct answer: 21

10C 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 on the inner surface of the shell is:

1. −7C
2. −3C
3. 0C
4. +3C

Correct answer: +3C

10C 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 on the outer surface of the shell is:

1. −7C
2. −3C

PHY101

1. 0C
2. +7C

Correct answer: +7C

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:

1. Q/4π0R2
2. Q/π0R2
3. 3Q/4π0R2
4. Q/8π0R2

Correct answer: Q/8π0R2

Positive charge Q is distributed uniformly throughout an insulating sphere of radius R, centered at the origin. A particle with positive charge Q is placed at x = 2R on the x axis. The magnitude of the electric field at x = R/2 on the x axis is:

1. Q/4π0R2
2. Q/8π0R2
3. Q/72π0R2
4. 17Q/72π0R2

Correct answer: Q/72π0R2

net electric flux in N · m2 /C through the inner surface of the shell is:

1. 0
2. Q/0
3. 2Q/0
4. Q/4π0

Correct answer: 0