PHY101 Final Term Solved Mega File by VUBuddy

PHY101 FINAL TERM SOLVED MEGA FILE VUSOLUTIONS

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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/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 ans: 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 ans: A

Q4. A cylinder has a radius of 2.1 cm and a length of 8.8 cm. Total Charge.1×10−7 C is distributed uniformly throughout. The volume charge density is:

1. 5.3 × 10−5 C/m3
2. 5.3 × 10−5 C/m2
3. 8.5 × 10−4 C/m3
4. 5.0 × 10−3 C/m3 E. 6.3 × 10−2 C/m3 ans: D
5. When a piece of paper is held with one face perpendicular to a uniform electric field the flux through it is 25N · m2 /C. When the paper is turned 25◦ with respect to the field the flux through it

is: A. 0 B. 12N · m2/C C. 21N · m2/C D. 23N · m2/C E. 25N · m2/C

Answer: D

Q6. The flux of the electric field (24N/C)ˆi + (30N/C)ˆj + (16N/C)ˆk through a 2.0m2 portion of the yz plane is:

1. 32N ·

m2 /C B. 34N · m2 /C C. 42N · m2 /C D. 48N ·

m2

/C E. 60N · m2 /C

Answer: D

Q7. Consider Gauss’s law: E · d A = q/0. Which of the following is true?

1. E must be the electric field due to the enclosed charge
2. If q = 0, then E = 0 everywhere on the Gaussian surface
3. If the three particles inside have charges of +q, +q, and −2q, then the integral is zero
4. on the surface E is everywhere parallel to d A

Correct answer: If the three particles inside have charges of +q, +q, and −2q, then the integral is zero

E. If a charge is placed outside the surface, then it cannot affect E at any point on the surface ans: C

Q8. A charged point particle is placed at the center of a spherical Gaussian surface. The electric flux ΦE is changed if:

1. the sphere is replaced by a cube of the same volume
2. the sphere is replaced by a cube of one-tenth the volume
3. the point charge is moved off center (but still inside the original sphere)
4. the point charge is moved to just outside the sphere E. a second point charge is placed just outside the sphere

Answer: D) the point charge is moved to just outside the sphere E. a second point charge is placed just outside the sphere

Q9. Choose the INCORRECT statement:

1. Gauss’ law can be derived from Coulomb’s law
2. 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
3. Coulomb’s law can be derived from Gauss’ law and symmetry
4. 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 ans: E

Q10. The outer surface of the cardboard center of a paper towel roll:

1. is a possible Gaussian surface
2. cannot be a Gaussian surface because it encloses no charge
3. cannot be a Gaussian surface since it is an insulator
4. cannot be a Gaussian surface because it is not a closed surface E. none of the above ans: D

Correct answer: cannot be a Gaussian surface because it is not a closed surface E. none of the above ans: D

Q11. 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. 0

1. 25 × 10−6
2. 2.2 × 105
3. 2.8 × 106

Correct answer: 2.8 × 106

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

Q12. 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:

1. is zero
2. is q/0
3. is q/40
4. is q/60

E. cannot be computed using Gauss’ law ans: E

Q13. 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:

1. 0
2. 7.1 × 104
3. 9.4 × 104
4. 1.4 × 105 E. 5.6 × 105

Answer: E

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

E. q/120 ans: D

15. 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

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

Answer: E

16. 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:

A. 0 B. 450 C. 900 D. 4500 E. 90, 000

Answer: C

17. 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:

A. 0 B. 4.2 C. 21 D. 280 E. can not tell without knowing the areas of the sides and bottom ans: C

Q18. 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