Homework 9 solutions
Physics 204, morning summer 2008
Chapter 22
Problems 40,59
Chapter 24
Problem 1
Chapter 25
Problems 5,2
40.
REASONING
The length of the wire is the number
N
of turns
times the length per turn.
Since each turn is
a square that is a length
L
on a side, the length per turn is 4
L
, and the total length is
N
(4
L
).
Since the area of
a square is
A
=
L
2
, the length of a side of the square can be obtained as
LA
=
, so that the total length is
()
4
NA
0
NA
.
The area can be found from the peak emf, which is
B
ξ
ω
=
, according to Equation 22.4.
Solving this expression for
A
and substituting the result into the expression for the total length gives
00
Total length
4
4
4
N
N
NB
B
⎜⎟
⎝⎠
⎛⎞
==
=
0
(1)
Although we are not given the peak emf
, we know that it is related to the rms emf, which is known:
0r
m
s
2
=
(Equation 20.13).
We are also not given the angular speed
ω
, but we know that it is related to
the frequency
f
in hertz according to
2
f
π
=
(Equation 10.6).
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 Spring '09
 rollino
 Physics, Total internal reflection, Specular reflection, Geometrical optics, total length, peak emf

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