Solution Q.1.

Which of the following statements is correct when the coil of a simple D.C. motor is vertical, i.e. at right angles to the magnetic field?

A. The magnetic flux is maximum and the torque is maximum.
B. The magnetic flux is maximum and the torque is zero.
C. The magnetic flux is zero and the torque is maximum.
D. The magnetic flux is zero and the torque is zero.


Answer: B

When the coil is vertical the lines of flux cut it at right angles so that the magnetic flux is maximum.
You can use the right hand palm rule or Fleming's Left Hand Rule to show that the force on the top and bottom of the coil is vertically up and down.
This produces no torque.

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