Ans to the even-numbered assigned problems in Ch 19--21
The following is a list of the answers to the even-numbered assigned problems.
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Chapter 19
19.6
(a) 0.206 mV
(b) 0.176 mV
19/8
(b) yes
(c) 3.88 
19.42
(a) 24.0 W
(b) 4.0 W
(c) 20.0 W
19.48 3R/2
19.50
(a) 0.80
(b) 17.5 A, 11.7 A, 5.8 A
(c) 35.0 A
(d) 28.0 V
(e) 1.60 : 490 W; 2.40 : 327 W; 4.80 : 163 W
(f) the one with the least resistance
19.52 5.00 ; 3.00 : 8.00 A; 6.00 : 4.00 A; 12.0 : 3.00 A; 4.00 : 9.00 A
19.60
(a) 2.00 A, to the left
(b) 5.00
(c) 42.0 V
19.66
(a) zero
(b) 500 V
(c) zero
(d) 0.111 A
(e) (a) 500 V; (b) zero; (c) 3.00 mC; (d) zero
19.72
(a) 0.471 A, counterclockwise
(b) 15.2 V
19.88 8.6 V
Chapter 20
20.4 1.91 T, eastward
20.8
(a) 1.53 × 10-3 N, -z direction
(b) 2.00 × 10-3 N, 140° counterclockwise from +x axis
20.14
(a) 1.35 mm
(b) speed is constant
(c) 1.88 × 1012 m/s2, toward center of curvature of path
(d) force perpendicular to velocity changes the direction of the velocity but not its magnitude
20.18
(a) 1.61 × 10-4 T, into page
(b) 1.11 × 10-7 s
(c) 0.294 T
20.20
(a) 22.7 m/s
(b) no
20.34
(b) Fcd = 1.20 N
(c) 0.420 N·m
20.50
(a) P: 4.1 × 10-5 T; Q: 4.1 × 10-5 T
(b) P: 9.0 × 10-6 T; Q: 9.0 × 10-6 T
20.64 0.0440 T
20.70 1750 turns
20.82
(a) point a
(b) 3.21 kg
20.86 1.70 × 10-4 T, out of the page
20.88
(a) 1.07 × 10-19 N, to the right
(b) 1.07 × 10-19 N, away from the wire
Chapter 21
21.4
(a) 0.0171 V
(b) 0.0285 A
21.12
(a) right to left
(b) right to left
(c) left to right
(d) no induced current
21.16
(a) counterclockwise
(b) counterclockwise
21.28 6.32 × 10-6 H
21.54
(a) 0.500 A
(b) 0.600 ms
(c) zero
21.62
(a) 0.641 A; zero
(b) 11.7 V; zero
(c) 1.03 mJ; 0.641 A
21.64
(a) 0.225 A, clockwise
(b) zero
(c) 0.225 A, counterclockwise
21.72
(a) 30.0 : zero; 20.0 : 3.00 A
(b) 30.0 : 2.00 A; 20.0 : 3.00 A
(c) 2.00 A
Lewis Ford
Physics Department
Texas A&M University
ford@physics.tamu.edu
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