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5
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A
square coil has  turns of wire, a resistance of  , and an area
of  . The magnetic flux passing through the coil
changes in such a way that a current  is induced flowing the right as shown. The magnetic field is directed into the
paper as shown. What is the change in
magnetic flux per second that creates this current and is the flux increasing
or decreasing
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Current going to the right implies
that the induced magnetic field is also into the paper so the magnetic flux
must be decreasing. So, solving for
the change in flux per time
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So Correct answer is D !
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6
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A
metal bar  , is sliding on
conductive rails to the right with a speed of
 . A
magnetic field is directed into the paper as shown below and has a strength
of  . The resistance of the light bulb is  . What is the magnitude and direction of the
current induced in the rails?
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Since the area is getting bigger,
the magnetic flux is getting larger.
So the induced B field needs to oppose the original B field, so it
must come out of the paper and therefore the current induced by the right
hand rule must go Counter Clockwise!
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So Correct Answer is D !
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7
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A
747 airplane is flying at a cruising speed of  due west.
The wingspan of the plane is  . The plane develops an induced emf  with the north wing being more positive than
the southern wing. What is the
magnitude and direction of the Earth’s vertical component of its magnetic
field in the area that the plane is currently flying?
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The magnetic force must be directed
north, since that is the more positive end, so  must point
north. Since  is pointing west,
and  must be
perpendicular to both and the force, must point up so
that west x up is north, by the right hand rule. Therefore, we know the direction of the
vertical component of the Earth’s magnetic field must be up! We are in the southern hemisphere!
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Solve for B
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So Correct Answer is A !
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8
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A
cylindrical solenoid has  turns of wire over a length of  and a radius of  . When a current of  is running through the wire, the solenoid
creates a magnetic field of  . How much energy is stored in the magnetic
field of the solenoid in the volume of the solenoid, which is found to be  ?
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So Correct Answer is A !
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Please send any comments or
questions about this page to ddonovan@nmu.edu
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This
page last updated on October 16, 2020
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