Physics 21
Fall, 2007
Practice Hour Exam #2
1
2
3
4
5
Total
Name:
Recitation Time
Recitation Leader
This exam is closed notes and closed book. You must show enough work on all problems to convince the grader
you understand how to solve the problem. You may use a calculator. Give units. There is an equation sheet on
the last page. All problems count 20 points.
Problem 1.
For the following circuit,
R
=8
.
0Ω
,
L
=2
.
0 mH, and
C
= 500
μ
F, and the frequency is
700 Hz.
R
L
C
V
rms
(a) Write the loop equation for this circuit.
(b) Draw a phasor diagram for the voltages in this
circuit. What is the rms value of the current if
V
rms
=6V?
(c) What is the phase relationship between the cur
rent and the applied ac voltage? In other words,
does the current lag or lead the applied voltage?
by how much?
Problem 2.
A single rectangular loop of wire with
the dimensions shown in the ±gure is inside a region of
magnetic ±eld
B
(
t
) directed into the page. The magni
tude
B
(
t
) of the ±eld is given by
B
(
t
)=0
.
02
t
T, where
t
is in seconds.
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 Spring '08
 Hickman
 Work, Magnetic Field, Energy density

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