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

1
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. 21 V
2. 18 V
3. 17 V
4. 24 V
5. 37 V

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2
A 48-turn circular coil (radius 4.1 cm, image
) is placed in a uniform magnetic field directed
perpendicular to the plane of the coil. The
magnitude of the magnetic field varies with time
as given by image where image is measured in
s. What is the magnitude of the induced current
in the coil at 0.10 s?

1. 1.9 A
2. 50 mA
3. 0.26 A
4. 1.5 A
5. zero

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3
A square loop (length along one side 21 cm)
rotates in a constant magnetic field which has a
magnitude of 2.0 T. At an instant when the angle
between the field and the normal to the plane of
the loop is equal to image and increasing at
the rate of image , what is the magnitude of
the induced emf in the loop?

1. 4.2 mV
2. 17 mV
3. 10 mV
4. 2.6 mV
5. 0.21 V

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4
A rectangular wire loop (length 54 cm, width
32 cm) lies completely within a perpendicular and
uniform magnetic field of magnitude of 0.7 T. If
the length of the loop starts increasing at a
rate of 22 mm/s at time image , while the width
is decreasing at the same rate, what is the
magnitude of the induced emf at time image ?

1. 6.0 mV
2. 5.4 mV
3. 7.9 mV
4. 3.9 mV
5. 14 mV

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5
A planar loop consisting of three turns of wire,
each of which encloses image , is oriented
perpendicularly to a magnetic field that
increases uniformly in magnitude from 16 mT to 31
mT in a time of 4.7 ms. What is the resulting
induced current in the coil if the resistance of
the coil is image ?

1. 36 mA
2. 12 mA
3. 0.18 mA
4. 7.0 mA
5. 65 mA

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6
A square coil (length of side 25 cm) of wire
consisting of two turns is placed in a uniform
magnetic field that makes an angle of image
with the plane of the coil. If the magnitude of
this field increases by 6.5 mT every 10 ms, what
is the magnitude of the emf induced in the coil?

1. 66 mV
2. 48 mV
3. 30 mV
4. 76 mV
5. 45 mV

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7
A long straight wire is parallel to one edge and
is in the plane of a single-turn rectangular loop
as shown. If the loop is changing width so that
the distance image changes at a constant rate
of 3.1 cm/s, what is the magnitude of the emf
induced in the loop at an instant when image ?
Let image , image , and image . applet

1. image
2. image
3. image
4. image
5. image

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8
The coil shown in the figure has 2 turns, a
cross-sectional area of image , and a field
(parallel to the axis of the coil) with a
magnitude given by image , where image is in
s. What is the potential difference, image , at
image ? image

1. - 7.1 V
2. 7.1 V
3. - 4.0 V
4. 4.0 V
5. - 19 V

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9
A circular loop ( image ) turns in a uniform
magnetic field with image . At an instant when
the angle between the magnetic field and the
normal to the plane of the loop is ( image )
rad and is decreasing at the rate of 0.52 rad/s,
what is the magnitude of the emf induced in the
loop?

1. 19 mV
2. 22 mV
3. 27 mV
4. 26 mV
5. zero

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10
A conducting rod (length 78 cm) rotates at a
constant angular rate of 17 revolutions per
second about a pivot at one end. A uniform field
( image ) is directed perpendicularly to the
plane of rotation. What is the magnitude of the
emf induced between the ends of the rod?

1. 1.9 V
2. 2.8 V
3. 1.1 V
4. 2.3 V
5. 1.5 V

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11
A 20-cm length of wire is held along an east-west
direction and moved horizontally to the north
with a speed of 2.9 m/s in a region where the
magnetic field of the earth is image directed
image below the horizontal. What is the
magnitude of the potential difference between the
ends of the wire?

1. image
2. image
3. image
4. image
5. image

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12
A rod (length 14 cm) moves on two horizontal
frictionless conducting rails, as shown. The
magnetic field in the region is directed
perpendicularly to the plane of the rails and is
uniform and constant. If a constant force of 0.60
N moves the bar at a constant velocity of 2.2
m/s, what is the current through the image -
image load resistor? applet

1. 0.32 A
2. 0.40 A
3. 0.26 A
4. 0.25 A
5. 0.36 A

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13
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. 38 mV
2. 77 mV
3. 25 mV
4. 2.8 mV
5. 0.81 mV

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14
In a region of space where the magnetic field of
the earth has a magnitude of image and is
directed image below the horizontal, a 51-cm
length of wire oriented horizontally along an
east-west direction is moved horizontally to the
south with a speed of 22 m/s. What is the
magnitude of the induced potential difference
between the ends of this wire?

1. 0.45 mV
2. 0.66 mV
3. 0.16 mV
4. 0.63 mV
5. 0.89 mV

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15
A conducting bar moves as shown near a long wire
carrying a constant 90-A current. If image ,
image , and image , what is the potential
difference, image ? applet

1. - 0.29 mV
2. 0.29 mV
3. - 0.51 mV
4. 0.51 mV
5. - 0.39 mV

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16
A bar ( image ) moves on two frictionless
rails, as shown, in a region where the magnetic
field is uniform ( image ) and out of the
paper. If image and image , what is the
magnetic force on the moving bar? image

1. 0.53 N to the left
2. 0.53 N to the right
3. 0.76 N to the left
4. 0.76 N to the right
5. None of the above

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17
A conducting bar of length image rotates with a
constant angular speed of 2.0 rad/s about a
pivot image at one end, as shown. A uniform
magnetic field (magnitude 0.19 T) is directed
into the paper. If image , what is the
potential difference, image ? image

1. 6.9 mV
2. - 6.9 mV
3. - 11 mV
4. 11 mV
5. - 14 mV

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18
A long solenoid (radius 3.3 cm, 2,600 turns per
meter) carries a current given by image , where
image is measured in s. When image , what is
the magnitude of the induced electric field at a
point which is 3.9 cm from the axis of the
solenoid?

1. image
2. image
3. image
4. image
5. image

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19
An electric field of image is induced at a
point 1.9 cm from the axis of a long solenoid
(radius 3.1 cm, 750 turns/m). At what rate is
the current in the solenoid changing at this
instant?

1. 0.50 A/s
2. 0.31 A/s
3. 0.74 A/s
4. 0.46 A/s
5. 0.28 A/s

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20
An AC generator consists of 6 turns of wire. Each
turn has an area of image . The loop rotates in
a uniform field ( image ) at a constant
frequency of 53 Hz. What is the maximum induced
emf?

1. 19 V
2. 3.1 V
3. 6.2 V
4. 14 V
5. 7.8 V

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21
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
2. if the loop moves at constant velocity while
   remaining perpendicular to and within the uniform
   magnetic field
3. if the loop moves at constant velocity in a
   direction parallel to the axis of the loop while
   remaining in the uniform magnetic field
4. if the loop is rotated through 180 degrees about
   an axis through its center and in the plane of
   the loop
5. in none of the above cases

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22
Coil 1, connected to a image resistor, sits
inside coil 2. Coil 1 is connected to a source of
50 cycle per second AC current. Which statement
about coil 2 is correct?

1. No current will be induced in coil 2.
2. DC current (current flow in only one direction)
   will be induced in coil 2.
3. AC current (current flow in alternating
   directions) will be induced in coil 2.
4. DC current will be induced in coil 2, but its
   direction will depend on the initial direction of
   flow of current in coil 1.
5. Both AC and DC current will be induced in coil 2.

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23
A bar magnet is dropped from above and falls
through the loop of wire shown below. The north
pole of the bar magnet points downward towards
the page as it falls. Which statement is correct?
image

1. The current in the loop always flows in a
   clockwise direction.
2. The current in the loop always flows in a
   counterclockwise direction.
3. The current in the loop flows first in a
   counterclockwise, then in a clockwise direction.
4. The current in the loop flows first in a
   clockwise, then in a counterclockwise direction.
5. No current flows in the loop because both ends of
   the magnet move through the loop.

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24
The alternating currents in power lines usually
cannot produce significant electrical currents in
human brains. Why not?

1. because power lines carry high current at high
   voltage
2. because power lines carry low current at high
   voltage
3. because power lines carry low current at low
   voltage
4. because power lines carry high current at low
   voltage
5. because power lines have high image (resistive)
   losses

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25
What is the correct form of Ampere's law for
circuits with gaps in them?

1. image
2. image
3. image
4. image
5. image

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26
A metal rod of length image in a region of
space where a constant magnetic field points into
the page rotates about an axis through its center
at constant angular velocity image . The ends,
image and image , make contact with a split
ring that connects to an external circuit. What
magnitude has the current in the external circuit
of resistance image ? applet

1. 0
2. image
3. image
4. image
5. image

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27
Two bulbs are shown in a circuit that surrounds a
region of decreasing magnetic field directed out
of the page. What happens when the switch is
closed? image

1. bulb 1 glows more brightly
2. bulb 2 glows more brightly
3. both bulbs glow equally brightly
4. bulb 1 goes out
5. bulb 2 goes out

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28
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. Crushing the loop.
2. Rotating the loop about an axis perpendicular to
   the field lines.
3. Keeping the orientation of the loop fixed and
   moving it along the field lines.
4. Pulling the loop out of the field.

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29
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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30
In the figure below, a given applied force of
magnitude image results in a constant speed
image and a power input image Imagine that
the force is increased so that the constant speed
of the bar is doubled to image image Under
these conditions, the new force and the new power
input are _____.

1. image and image
2. image and image
3. image and image
4. image and image

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31
The figure below shows a magnet being moved in
the vicinity of a solenoid connected to a
sensitive ammeter. The south pole of the magnet
is the pole nearest the solenoid, and the ammeter
indicates a clockwise (viewed from above) current
in the solenoid. image We can make the
conclusion that the person is _____.

1. inserting the magnet
2. pulling the magnet out

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32
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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