Selected Solutions, Physics 104 Exam File

Electric force, fields, and dipoles 
1. 12cm
3. c and d
5. 53o below the horizon
7. 2.6
mN/C, 150o
9. 5.8MN/C, to the left
13. 24.3N, neg. x
19. 2´10-11C×m, 0.36N/C, positive y-direction
Electrical potential and capacitance 
1. 15V/m at -63o
3. a) and b) 
5. a) V/m2
7. 47MV/m at 17o, 94000N, 18MV, 36kV
9. 0V, 120kV/m, 1.2×1010V/m, ditto
11. zero, 540kV, 54MV/m
17. -800V, x=0 wall, 0.24m
21. 3.9´10-11m, 0.75mJ
23. properties of space, scalars
25. -7500V
29. 0, +540V, -54kV/m
31. 149.2V, 147.8V, 70V/m, 74V/m, 0
33. 120MN/C at 0o, 5.941MV, 5.939MV, 100MV/m
35. 0.8mV, 38nC
37. 37micron, 1.3mC, 73kV/m
37. 0.034m2, 27nC, no sparking
39. 0.89pF, 75kV, 67nC, 1.1pF
Electric current, resistance, circuits
1. 4 resistors in parallel
3. 36microC, 3.6ms, 1.4m2
5. 1800J, 12eV, 1.9´ 7. V/2, 3R
9. Voltage decreases to 71% of its value 
11. 2V/m, 39n
W m
17. It decays exponentially toward zero. 
21. 3.0s, 0.76mC, 1.2´ 10-8C× m
23. decaying, decaying, increasing, constant
Magnetism 
1. East to West
3. -5x10-13T, +10x10-13T, 7x10-13T
5. North
7. 240MA, 1.1micron/s
9. 20microT, 24microN
11. 0.0017T, 250
mN, toward top of page
Magnetic Induction 
1. Counter-clockwise
3. to the right of the page
5. bottom of the page, counterclockwise
7. toward top of page, out of the page
9. 2800N, 6.3MA-m2
11. 14s, clockwise
13. 23
mT into page, 9.8mN toward top of page
15. 14s. clockwise
17. counter-c'wise, 5.5s, 0.94
mT
19. 0A, 0.60A; 12V, 0V; 1.3ms; 0.52A
21. 12mA, 80
ms, 21ms
AC Circuits 
1. 156V, 7.6ohm, 350microF
3. 0.35A, 0.25A; 12W, 6W; 0.26H
5. 6.45V
7. 6.1A, 163V, 1000W
9. 14W, 10.7V, 1.9A, 1.3A
11. 9.8
W, 490mH, 5.1mF
13. 1.5nH, 1.5nF, 1
W, 0.03W
15. 22000
17. 990kV, 6GW, 3GW, 1:6400; 30MA
19. 400, 0.010A, 0.014A, 2.4W
Geometric Optics 
1. 22ms
3. 22o from the vertical, 36cm
5. 7.6o, 82.4o, 1.487
7. 2.01´ 108m/s, 1.52´ 10-11s, 79o
9. -1.5m, 0.25, virtual
11. The first three
13. 9.3cm
15. 60m, 1.5
17. -1.3m, -0.77D, 13cm
19. +4.0D, 2.3cm
23. 12.5cm, 8.3cm
25. 0.40m, 0.67m
Physical Optics 
1. interference, accommodation, reflecting material has larger refractive index
3. F, T, F
5. 41.8o
11. Soap bubble, black: all light is poorly reflected, 92nm, none
13. "soap bubble", white, 183nm, 370nm
15. 0.4m, 8, three
17. bubble, black, 98nm, none
19. 53o, 7, 7
21. 25o, 9cm
Relativity 
1. 0.9999c, 5000lb, 0.35cm, 6.1moc2
3. TTFTT
5. No, no. Consider the centripetal acceleration.
7. 2.3, 0.83 (ux=-0.83c), 42m
9. 0.995c, 9cm, 8.3cm
11. c
13. 10.0005m, 8000.4kg, 3.6×1016J, 0.4kg
15. 2.1´ 17. -0.99995c, 7000kg, 0.25cm, 6.1moc2
19. 0.42m/s2
21. -0.65c, 1.25´ 23. 1.6´ 10-28kg, 104MeV, no
Modern Physics 
1.
lp=9.7mm, 4%
3. 2.8
5. 3, 2.9
7. 2.14eV, 1.14´ 15. -2.40eV, -2.00eV, -1.60eV, -1.20eV
17. 6, 3.3´ 10-25N× s, 76.5
mm
19. 1.1´ 29. lower limit: 1.7fm, 0.13fm
31. 35m/s, 6.3´ 10-11m
45. 0.1587u, 147.8Mev, 0.134MeV, released
47. 8´ 10-16m, 10fm
49. 1.94u, 1807MeV, 84MeV
53. 103MeV given off, 181MeV
55. 14hr