Download Magnetism Test Review

Magnetism Test Review:
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Name:__________________
What happens if you cut a magnet in half?
A. you get monopoles
B. it becomes demagnetized
C. you get a separate south pole and a separate north pole
D. you get two magnets, each magnet having both north and south poles
A positive charge +Q that is moving to the right is located in a magnetic field B that is directed into this sheet as
shown in the diagram below. Which arrow represents the direction of the magnetic force on the charge?
x
x
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x
xB
x
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x +Q x
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If a proton is released at the equator and falls toward the Earth under the influence of gravity, the magnetic force on
the proton will be toward the:
A. north
B. south
C. east
D. west
An electron is moving at 3.00 x 105 m/s in the positive x direction. A magnetic field of 0.800 T is in the positive z
direction. What is the magnetic force on the electron?
A. 3.84 x 10-14 N in the negative z direction
B. 3.84 x 10-14 N in the positive z direction
-14
C. 3.84 x 10 N in the negative y direction
D. 3.84 x 10-14 N in the positive y direction
A wire is lying horizontally in the north-south direction and the horizontal magnetic field is toward the east. The
current in the wire is directed to the south. What is the direction of the magnetic force on the wire?
N
A. East
B. Down, into the page
W
E
C. Up, out of the page
D. West
S
Which of the following correctly describes the right-hand rule for current-carrying wire placed in a magnetic field?
A. When the fingers of the right hand are pointed in the direction of the B vector and then turned or curled the
direction of the conventional current I, the extended thumb points in the direction of the force on the wire.
B. When the fingers of the right hand are pointed in the direction of the B vector and then turned or curled the
direction of the conventional current I, the force is where the palm was facing before the fingers were curled.
C. When the fingers of the right hand are pointed in the direction of the conventional current I and then turned or
curled toward the B vector, the force is where the palm was facing before the fingers were curled.
D. When the fingers of the right hand are pointed in the direction of the conventional current I and then turned or
curled toward the B vector, the extended thumb points in the direction of the force on the wire.
How should a current-carrying wire be oriented in the magnetic field in order for it to experience the maximum
magnetic force due to the field?
A. The wire should make an angle of 45 with the magnetic field.
B. The wire should make an angle of 90 with the magnetic field.
C. The wire should be parallel to the field such that the conventional current is in the same direction as the field.
D. The wire should be parallel to the field such that the conventional current is opposite to the direction of the
field.
A bar magnet is passed through a coil of wire. The induced current is greatest when
A. the magnet moves slowly so that it is inside the coil for a long time
B. the magnet moves fast, so that it is inside the coil for a short time
C. the north pole of the magnet enters the coil first
D. the south of the magnet enters the coil first
The magnetic flux through a wire loop in a magnetic field B does NOT depend on
A. the area of the loop
B. the shape of the loop
C. the magnitude of the field
D. the angle between the plane of the loop and the direction of B
10. A transformer has 100 turns in its primary winding and 300 turns in its secondary. If the power input to the
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transformer is 60 W, the power output is
A. 20 W
B. 60 W
C. 180 W
D. 540 W
In a transformer, the primary coil has thrice as many loops as the secondary coil. This is a ___________ transformer.
A. step-down
B. voltage
C. reduction
D. step-up
A transformer goes from 10 V to 5000 V. How do the number of loops relate in the different coils?
a. There are 500 times more loops in the primary coil.
b. There are 5000 times more loops in the primary coil.
c. There are 500 times more loops in the secondary coil.
d. There are 50 times more loops in the secondary coil.
In a mass spectrometer, an ion will have a smaller radius for its circular path if
e. its speed is greater.
C. its charge is greater.
f. its mass is greater.
D. the magnetic field is weaker.
The path of a charged particle moving parallel to a uniform magnetic field will be:
g. straight line.
C. ellipse.
h. circle.
D. parabola.
Problems: Answer on a separate sheet of paper: You must show all work for any credit!!! This
includes formulas, variables, calculations, and final answers with the correct units!
15. A magnetic field, which has an intensity of B = 0.950 T, is directed vertically downward. An electron is moving
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horizontally through the field from left to right at v = 12,000 m/s. What will be the direction of the magnetic force
acting on this electron?
A proton is moving with a velocity of v = 21,000 m/s through a uniform magnetic field such that the proton moves in
a circular path which has a radius of r = 4.50 cm. What is the strength of the magnetic field B?
Consider a single loop of wire which encloses an area of A = 50.0 square centimeters. A magnetic field, which is
parallel to the normal of this loop, initially has an intensity of B = 0.220 Tesla. Over a time period of t = 0.200
seconds the magnetic field strength B drops to zero. What will be the resulting EMF in the loop?
A transformer is made by winding a primary coil of 300 turns around an iron core. A secondary winding of 750 turns
is made about the same core. If the primary voltage is 120 V, what is the output voltage on the secondary?
A current-carrying wire of length 50 cm is positioned perpendicular to a uniform magnetic field. If the current is 10.0
A and it is determined that there is a resultant force of 3.0 N on the wire due to the interaction of the current and
field, what is the magnetic field strength?
An electron moving at 5.6 x 107 m/s travels through a uniform magnetic field of 1.4 T at right angles to the field.
How strong is the force that acts on the electron?
How much current is flowing in 420-cm long wire if the maximum force on it is 0.900 N when placed in a uniform
0.0800-T field?
A beam of singly ionized oxygen atoms is sent through a mass spectrometer. The values are B = 7.2 x 10 -2 T, q =
1.60 x 10-19 C, r = 0.085 m, and V = 110 V. Find the mass of an oxygen atom.
A stream of singly ionized atoms is not deflected as it passes through a 3.5 x 10 -3-T magnetic field perpendicular to a
2.8 x 102-V/m electric field. What is the speed of the atoms as they pass through the crossed fields?
A proton moves at a speed of 4.9 x 104 m/s as it passes through and is perpendicular to a 0.50-T uniform magnetic
field. What is the radius of the circular path?
A step-up transformer has 400 turns on its primary coil and 1000 turns on its secondary coil. If the secondary coil has
a current of 1.30 A, what is the current in the primary coil?
A square wire loop 5 cm on a side is perpendicular to a magnetic field of 0.08 T. If the field drops to 0 in 0.2 s, the
average emf induced in the loop during that time is
A coil contains 100 turns of wire in a loop 15 cm in diameter. The loop is placed between the poles of a large
electromagnet, B = 1.0 T, with the plane of the loop perpendicular to the field. If the magnetic field is steadily
reduced from 1.0 T to 0 in 16 s, what is the average emf in the coil while the field is changing?
The primary winding of a transformer has 200 turns and its secondary winding has 50 turns. If the current in the
secondary winding is 40 A, the current in the primary is?