Ch.15 Physics

1. When a glass rod is rubbed with silk, which of the following statements best describes what happens?
   1. Electrons are removed from the rod.
   2. Protons are removed from the silk.
   3. The silk is charged positively.
   4. The silk remains neutral.
2. Which of the following best characterizes electrical insulators?
   1. charges on the surface don't move
   2. high tensile strength
   3. electric charges move freely
   4. good heat conductors
3. I wish to use a positively charged rod to charge a ball by induction. Which statement is correct?
   1. The charge on the ball will be positive.
   2. The ball must be a conductor.
   3. The ball must be an insulator that is connected temporarily to the ground.
   4. The ball is charged as the area of contact between the two increases.

1. If the size of the charge value is tripled for both of two point charges maintained at a constant separation, the mutual force between them will be changed by what factor?
   1. 9
   2. 3
   3. 1/3
   4. 1/9
2. Two electrons are separated by 7.0 cm. What is the ratio of the electric force to the gravitational force between them? (m_e = 9.11 10³¹ kg, k_e = 8.99 10⁹ Nm²/C², G = 6.67 10^-11 Nm²/kg², and e = 1.6 10¹⁹ C)
   1. 2.3E+2
   2. 1.3E+20
   3. 3.1E+22
   4. 4.2E+42
3. A 7.0-C charge is placed at the origin and a second charge is placed on the xaxis at x = 0.3 m. If the resulting force on the second charge is 6.9 N in the positive x-direction, what is the force on the charge at the origin?
   1. 6.9 N in the positive x-direction
   2. 6.9 N in the negative x-direction
   3. 0 N
   4. not able to be determined until the second charge is known

1. An electron with a charge value of 1.6 10¹⁹ C is moving in the presence of an electric field of 400 N/C. What force does the electron experience?
   1. 8.0E-21 N
   2. 6.4E-22 N
   3. 6.4E-17 N
   4. 4.0E+17 N
2. A proton initially moves left to right along the x-axis at a speed of 9.0 10³ m/s. It moves into an electric field, which points in the negative x direction and travels a distance of 0.8 m before coming to rest. If the proton's mass and charge are 1.67 10²⁷ kg and 1.60 10¹⁹ C respectively, what is the magnitude of the electric field?
   1. 4.3E+1 N/C
   2. 5.3E-2 N/C
   3. 5.3E-1 N/C
   4. 6.6E-1 N/C
3. An electron with a speed of 2.0 10⁶ m/s moves into a uniform electric field of 550 N/C that is parallel to the electron's motion. How long does it take to bring the electron to rest? (me = 9.11 10³¹ kg, e = 1.6 10¹⁹ C)
   1. 2.1E-8 s
   2. 6.4E-9 s
   3. 1.6E-6 s
   4. 1.6E-6 s

1. Q₁ has 50 electric field lines radiating outward and Q₂ has 250 field lines converging inward. What is the ratio Q₁/Q₂?
   1. 5
   2. 5
   3. 1/5
   4. 1/5
2. A spherical volume of space has an electric field of intensity 130 N/C directed radially outward from it surface of radius 0.4 m. What is the net charge enclosed within this surface? (₀ = 8.85 10^-12 F/m)
   1. 3.5 nC
   2. 2.3 nC
   3. -3.5 nC
   4. -2.3 nC

1. A conducting spherical shell of inner radius r₁ and outer radius r₂ has a charge Q on it. An additional charge, also Q, is then added to the sphere. What is the resulting charge per unit area on the outer surface of the sphere?
   1. b. No answer given is correct.

c. d.

Ch 16

1 . A proton (+1.6 10¹⁹ C) moves 20 cm on a path in the direction of a uniform electric field of strength 2.4 N/C. How much work is done on the proton by the electrical field?

1. 7.7E^-20 J
2. 7.7E^-20 J
3. 1.8E^-19 J
4. 8.6E^-20 J

1. If an electron is accelerated from rest through a potential difference of 1 200 V, find its approximate velocity at the end of this process. (e = 1.6 10¹⁹ C; m_e = 9.1

10³¹ kg)

1. 2.5E+7 m/s
2. 2.1E+8 m/s
3. 2.1E+7 m/s
4. 4.2E+7 m/s
5. An electron in a cathode ray tube is accelerated through a potential difference of 8.0 kV. What kinetic energy does the electron gain in the process? (e = 1.6

10¹⁹ C)

1. 1.0E-15 J
2. 1.3E-15 J
3. 1.0E-21 J
4. 5.0E-16 J
5. A 10-V battery moves 7.0 mC of charge through a circuit running from its positive terminal to its negative terminal. How much energy was delivered to the circuit?
6. 1.4 mJ
7. 0.67 J
8. 0.070 J
9. 5.7E+2 J
10. Four point charges are on the rim of a circle of radius 10 cm. The charges are (in C) +0.50, +1.5, 1.0, 0.50. If the electrical potential at the circle's center due to the +0.5 charge alone is 4.5 10⁴ V, what is the total potential at the center due to the four charges combined?
11. 18 10⁴ V
12. 4.5 10⁴ V
13. zero
14. 4.5 10⁴ V
15. Two point charges of values +3.6 and +6.9 C are separated by 0.40 m. What is the electrical potential at the point midway between the two point charges? (k_e = 8.99 10⁹ Nm²/C²)
16. +0.47 MV
17. 0.24 MV
18. +0.24 MV
19. +0.97 MV
20. Suppose two equipotential surfaces are the planes x = 3 m and x = 5 m. If the potential at the x = 3 m surface is 10 V and the potential at the x = 5 m surface is 50 V, what is the magnitude of the electric field between the two surfaces?

a. 40 N/C	b. 20 N/C
c. 15 N/C	d. 10 N/C

1. Equipotential surfaces around a point charge are

a. spherical. b. cylindrical.

c. planar. d. none of these choices.

1. A parallel-plate capacitor has a capacitance of 25 F. What potential difference across the plates is required to store 7.2 10⁴ C on this capacitor?
2. 2.9E+1 V
3. 3.6E+1 V
4. 4.5E+9 V
5. 2.9E-1 V

1. Two point charges of values +2.0 and +5.5 C, respectively, are separated by

0.50 m. What is the potential energy of this 2-charge system? (k_e = 8.99 10⁹

Nm²/C²)

1. +0.50 J
2. 0.20 J
3. +0.20 J
4. 0.41 J
5. At what distance from a point charge of 8.0 C would the electrical potential be 4.8 10⁴ V? (k_e = 8.99 10⁹ Nm²/C²)
   1. 1.8 m
   2. 0.43 m
   3. 1.5 m
   4. 5.4 m
6. Two particles, each of charge 2.5 10^-19 C, are 4.8 10^-5 m apart. What is the change in potential energy if they are brought 2.4 10^-5 m closer together? (k_e = 8.99 10⁹ Nm²/C²)
   1. 1.2E-23 J
   2. 4.7E-24 J
   3. 2.3E-16 J
   4. 1.4E-15 J

Ch 17

1. The current in an electron beam in a cathode-ray tube is measured to be 50 A. How many electrons hit the screen in 7.0 s? (e = 1.6 10¹⁹ C)
   1. 4.4 10¹¹ electrons
   2. 3.5 10¹³ electrons
   3. 2.2 10¹⁵ electrons
   4. 3.1 10¹⁸ electrons
2. The charge flowing through a light bulb attached to a 12.0-V battery in 11.0 s is 30.0 C. What is the total energy delivered to the filament during this process? a. 12.0 J
   1. 360 J
   2. 3 960 J
   3. 132 J

3. The charge flowing through a light bulb attached to a 12.0-V battery in 13.0 s is 30.0 C. What is the average power supplied by the battery during this process?

a. 360 W

1. 12.0 W
2. 27.7 W
3. 5.20 W
4. A 300-Ah battery can deliver how many coulombs starting from a full charge?
   1. 4.8 10³ b. 4.3 10⁴

c. 7.2 10⁵ d. 1.1 10⁶

1. If a metallic wire of cross-sectional area 4.0 10⁶ m² carries a current of 7.0 A and has a mobile charge density of 4.24 10²⁸ carriers/m³, what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 10¹⁹ C)
   1. 1.8E+3 m/s
   2. 1.7E+3 m/s
   3. 4.1E-4 m/s
   4. 2.6E-4 m/s
2. When an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field?
   1. must be zero
   2. must be parallel to the current flow
   3. must be antiparallel (opposite direction) to the current flow
   4. must be perpendicular to the current flow
3. A high-voltage transmission line of diameter 2 cm and length 150 km carries a steady current of 1 000 A. If the conductor is copper with a free charge density of 8 10²⁸ electrons/m³, how long does it take one electron to travel the full length of the cable? (e = 1.6 10¹⁹ C)
   1. 6.0 10² s
   2. 6.0 10⁴ s
   3. 6.0 10⁶ s
   4. 6.0 10⁸ s
4. A beam of protons in an accelerator incident on a metal plate carries a current of 150 A. How many protons strike the plate in 24.0 s?
   1. 1.60E+5
   2. 3.60E+9
   3. 2.25E+16
   4. 3.91E+13