barron (jmb7952) – Practice Midterm 03 – yao – (56125)
1
This
print-out
should
have
18
questions.
Multiple-choice questions may continue on
the next column or page – find all choices
before answering.
001
10.0points
A 1
.
68 H inductor carries a steady current
of 0
.
518 A.
When the voltage source in the
circuit is shorted out, the current disappears
in 15
.
1 ms.
What is the average induced
emf
in the
inductor during this time?
Answer in units of V.
002
10.0points
How does the current in the secondary of the
transformer compare with the current in the
primary when the secondary voltage is twice
the primary voltage?
I
≈
2
V
rms
1.
the same as the current in the primary
L
R
t
R
b
C
V
rms
Find the
rms
current
I
delivered by the
power supply when the frequency is very
small.
1.
I
≈
V
rms
(
R
t
+
R
b
)
R
t
R
b
2.
I
≈
2
V
rms

2.
twice the current in the primary

3.
Sometimes these two currents are not

related to each other.
4.
half the current in the primary

003
10.0points
What is the
rms
current?

What current is required in the windings
of a long solenoid that has 2040 turns uni-
formly distributed over a length of 0
.
168 m
in
order
to
produce
a
magnetic
field
of
magnitude 0
.
000316 T at the center of the
solenoid?
The permeability of free space is
4
π
×
10
−
7
T
·
m
/
A
.
Answer in units of mA.
004
10.0points
Consider the circuit