Physics 2220.004
Spring 2006
Examination 3
Name:
This test consists of 8 multiplechoice questions and 5 freeresponse problems, for a total of 110
points (so that 10 points of extra credit are possible).
To receive credit for the freeresponse
problems, you must show all of your work on the pages provided.
Don’t hand in any extra sheets
or other paper.
You may also earn partial credit for the some of the multiple choice problems if
you show your work.
Suggested procedure for solving the problems:
1.
Read each problem carefully and make sure you know what is being asked before
starting the problem.
2.
Draw a figure for the problem.
3.
List the parameters given.
4.
Write down the equations to be used.
5.
Solve for the answer symbolically.
6.
Substitute numbers into you final equation and circle your answer.
WORK THE EASY PROBLEMS FIRST!!
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(5 points) In an overhead straight wire, the current is north.
The magnetic field due to this
current, at our point of observation, is
a)
east
b)
up
c)
north
d)
down
e)
west
2.
(5 points) A closed loop of wire in a horizontal plane is lowered vertically
over a permanent magnet oriented with its south pole up.
Viewed from
above, as the wire loop is lowered from above the magnet to below the
magnet (so that the magnet passes through the loop),
a)
a current is induced in the clockwise direction only.
b)
a current is induced in the counterclockwise direction only.
c)
a current is first induced in the clockwise direction, then in the counterclockwise
direction.
d)
a current is first induced in the counterclockwise direction, then in the clockwise
direction.
e)
no current flows in the wire because there is no source of
emf
in the circuit.
3.
(5 points) A permanent magnet is dropped through a vertical conducting tube and is observed
to fall very slowly, as was demonstrated in class.
The same magnet is now dropped through
a second vertical tube and is observed to fall approximately as fast as it would without the
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 Fall '00
 Littler
 Physics, Magnetic Field, 4.0 cm, 0.800 m, 3.00 cm, 2.00 cm, 0.750 m

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