A simple motor consists of a flat rectangular coil with n turns in a magnetic field B
as shown.
B = 0.1 T
1A
X
Y
0.01 m2
The coil has an area of 0.01 m2 and carries a current of 1 A. The motor drives a pulley
of diameter 20 cm, and weights can be hung from either side of the pulley at point X
or point Y.
(a)
In order to prevent rotation, should a weight be hung at point X or at point Y?
Justify your answer.
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(b)
What is the magnitude of the torque provided by a mass of 0.2 kg suspended
from either point X or point Y ?
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(c)
If the motor is just stopped by a mass of 0.2 kg, how many turns does the coil
have?
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