Transcript A coil is wrapped with 340 turns of wire on the perimeter of a circular

A coil is wrapped with 340 turns of wire on the perimeter of a circular frame (radius =
8.1 cm) . Each turn has the same area, equal to that of the frame. A uniform
magnetic field is turned on perpendicular to the plane of the coil. This field changes
at a constant rate from 20 to 80 mT in a time of 20 ms. What is the magnitude of the
induced emf in the coil at the instant the magnetic field has a magnitude of 50 mT?
1.
2.
3.
4.
5.
21 V
18 V
17 V
24 V
37 V
20% 20% 20% 20% 20%
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2.
3.
4.
5.
1.9 A
50 mA
0.26 A
1.5 A
zero
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3.
4.
5.
4.2 mV
17 mV
10 mV
2.6 mV
0.21 V
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5.
6.0 mV
5.4 mV
7.9 mV
3.9 mV
14 mV
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5.
36 mA
12 mA
0.18 mA
7.0 mA
65 mA
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66 mV
48 mV
30 mV
76 mV
45 mV
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20% 20% 20% 20% 20%
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5.
- 7.1 V
+ 7.1 V
- 4.0 V
+ 4.0 V
- 19 V
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19 mV
22 mV
27 mV
26 mV
zero
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1.9 V
2.8 V
1.1 V
2.3 V
1.5 V
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0.32 A
0.40 A
0.26 A
0.25 A
0.36 A
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A conducting rod (length = 2.0 m) spins at a constant rate of 1.8 revolutions per
second about an axis that is perpendicular to the rod and through its center. A
uniform magnetic field (magnitude = 6.8 mT) is directed perpendicularly to the plane
of rotation. What is the magnitude of the potential difference between the center of
the rod and either of its ends?
1.
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4.
5.
38 mV
77 mV
25 mV
2.8 mV
0.81 mV
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0.45 mV
0.66 mV
0.16 mV
0.63 mV
0.89 mV
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- 0.29 mV
+ 0.29 mV
- 0.51 mV
+ 0.51 mV
- 0.39 mV
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0.53 N to the left
0.53 N to the right
0.76 N to the left
0.76 N to the right
None of the above
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+ 6.9 mV
- 6.9 mV
- 11 mV
+ 11 mV
- 14 mV
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20% 20% 20% 20% 20%
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0.50 A/s
0.31 A/s
0.74 A/s
0.46 A/s
0.28 A/s
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19 V
3.1 V
6.2 V
14 V
7.8 V
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When will the magnetic flux through a
loop perpendicular to a uniform magnetic
field change?
1.
if the loop is replaced by two loops,
each of which has half of the area of
the original loop
if the loop moves at constant velocity
while remaining perpendicular to and
within the uniform magnetic field
if the loop moves at constant velocity in
a direction parallel to the axis of the
loop while remaining in the uniform
magnetic field
if the loop is rotated through 180
degrees about an axis through its
center and in the plane of the loop
in none of the above cases
2.
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5.
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1.
2.
3.
4.
5.
No current will be induced in coil 2.
DC current (current flow in only
one direction) will be induced in
coil 2.
AC current (current flow in
alternating directions) will be
induced in coil 2.
DC current will be induced in coil
2, but its direction will depend on
the initial direction of flow of
current in coil 1.
Both AC and DC current will be
induced in coil 2.
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1.
The current in the loop always flows in a clockwise
direction.
The current in the loop always flows in a
counterclockwise direction.
The current in the loop flows first in a
counterclockwise, then in a clockwise direction.
The current in the loop flows first in a clockwise,
then in a counterclockwise direction.
No current flows in the loop because both ends of
the magnet move through the loop.
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The alternating currents in power lines usually
cannot produce significant electrical currents in
human brains. Why not?
1.
2.
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What is the correct form of Ampere's
law for circuits with gaps in them?
1.
2.
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20% 20% 20% 20% 20%
1.
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5.
bulb 1 glows more brightly
bulb 2 glows more brightly
both bulbs glow equally
brightly
bulb 1 goes out
bulb 2 goes out
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A circular loop of wire is held in a uniform magnetic
field, with the plane of the loop perpendicular to the field
lines. Which of the following will not cause a current to
be induced in the loop?
1.
2.
3.
4.
Crushing the loop.
Rotating the loop about
an axis perpendicular to
the field lines.
Keeping the orientation of
the loop fixed and moving
it along the field lines.
Pulling the loop out of the
field.
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Suppose you would like to steal power for your home
from the electric company by placing a loop of wire near
a transmission cable, so as to induce an emf in the loop
(an illegal procedure). What should you do?
1. Place your loop so
that the transmission
cable passes through
your loop.
2. Simply place your
loop near the
transmission cable.
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25% 25% 25% 25%
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50%
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2.
50%
inserting the magnet
pulling the magnet out
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In a region of space, the magnetic field increases at a
constant rate. This changing magnetic field induces an
electric field that _____.
1. increases in time
2. is conservative
3. is in the direction of
the magnetic field
4. has a constant
magnitude
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