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Physics 213
Practice Final
Fall 2007
page 1 of 13
ANSWER KEY
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Practice Final
Fall 2007
page 2 of 13
1.
True/False
[10 points]
Indicate T (True) or F (False) in the space at left for each of the following statements.
__F__
An appropriate unit for impedance is Ohm
second (Ω
s).
__T__
The magnetic forces between the adjacent coils of a solenoid act to decrease the solenoid length
and increase its radius.
__F__
The integral of
B
d
A
over a closed surface, in the case of a uniform magnetic field, is equal to
the total surface area times the magnetic field magnitude.
_T___
A charged particle subject only to magnetic forces has constant kinetic energy.
__F__
To cause a timevarying magnetic flux through a circular loop confined to a region with a
uniform magnetic field
B
, you can move the loop in a direction perpendicular to
B
.
__T
__
A bar magnet dropped into the top of a vertical aluminum tube will be emerge from the tube’s
bottom more slowly than a nonmagnetic bar dropped through the tube.
__F__
The asymptotic current in an RL circuit powered by an ideal battery with emf
E
depends on the
values of all of R, L and
E
.
__T__
The ratio of units [E]/[B] is
“meters / second” in the MKS system.
__T__
In an AC circuit, a capacitor is effectively "invisible" at very high frequency, i.e. virtually
indistinguishable from an ideal conductor.
__F__
The peak power in an AC circuit is given by the average power multiplied by
2
.
Physics 213
Practice Final
Fall 2007
page 3 of 13
2.
[3 points]
A conductor has electrons as the charge carrier of electric current. You
place the conductor in a region containing a uniform magnetic field in
the positive z direction (
B
B
ˆ
k
, out of page).
If you
run an electric
current in the positive x direction (
J
J
ˆ
i
) through your conductor, then
a Hall effect voltage difference would result from an electric field in
what direction?
1. +x direction
2.
–
x direction
3. +y direction
4.
–
y direction
5. +z direction (out of page)
6.
–
z direction (into page)
Answer: ____4__________
3.
[3 points]
Equal electric currents
I
flow in opposite directions in wires
that pass through the plane of this page.
For the path in the
plane of this page shown at right, what is the value of
∮
B
•
dl
around the path?
1. 2μ
0
I
2. μ
0
I
3. 0
4.
–
μ
0
I
5.
–
2μ
0
I
Answer: _____4_________
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View Full DocumentPhysics 213
Practice Final
Fall 2007
page 4 of 13
4.
[7 points]
An ideal battery with an emf
E
is connected to the circuit shown at
right. Suppose that the top switch has been closed for a very long
time.
A) (3 points) What is the value of the current (
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This note was uploaded on 08/27/2009 for the course PHYS 2213 taught by Professor Perelstein,m during the Fall '07 term at Cornell University (Engineering School).
 Fall '07
 PERELSTEIN,M
 Physics, Magnetism, Heat

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