7
(b)
B
=
=
=
o qv
r
2
4 |r|
(1 107
Tm
A )(1.6
1019 C)( 3 104 , 2 104 , 7 104 m/s) 0.625, 0.625, 0.469
(6.4 103 )2
1.34 107 , 2.26 1017 , 1.22 1017 T
18.X.39
(a) Conventional current ows N. Use the right-hand rule with your thumb in the direction of the
7
19.P.42
(a) Electrons move to the right. Their magnetic eld must point toward the top of the page.
(b) The current divides equally between bulbs 2 and 3 since they are identical. Thus the current through each of them is
18
1.5 10 e/s.
(c) B2 = B3 < B1
(
13
(2) Quasi-steady state: magnitude of E is uniform throughout the wire, drives current in the direction to reduce charge on
capacitor plates (top plate gets less positive, bottom plate gets less negative). There may be some excess charge on the
bends, b
7
21.X.35
F is toward the center of the circle. The right-hand rule shows that B is outward, in the +z direction, so B =< 0, 0, 1 >.
Fnet
Fmag
qvB
qB
B
dp
dt
dp
=
dt
mv 2
=
R
mv
=
R
mv
=
qR
m 2R
T
=
qR
m2
=
qT
4(1.67 1027 kg)2
=
2(1.6 1019 C)(80 109 s)
=
Physics 115: CONTEMPORARY PHYSICS III
Spring 2012
Prof. Michael S. Vogeley
HOMEWORK 8 SOLUTIONS
1. Water wave
The height of a water wave is
y = (1.5m) cos [(25.1/s)t (2.51/m)x + /2]
Calculate the angular frequency , the frequency f , the period T , the wa