Operation of a DC Motor – Practice


1) A DC motor consists of a coil that contains 200 loops and its plane is at an angle of 60° to the direction of a magnetic field. The magnetic field has a strength of 0.8T. The coil has dimensions of 8cm by 15cm and a 250 mA current passes through the coil.

a) Determine the magnitude of the torque acting on the coil:

b) What is the maximum torque this coil could produce:

2) A 10cm square coil has a current of 4.00A running through it. The coil is exposed to a magnetic field as shown below with a strength of 0.05T. The coil experiences a maximum torque of 0.16Nm.

a) Determine the number of turns on the coil

b) Which direction does the coil turn

3) The coil below forms a DC motor and is rotated through 360° from the starting position shown below. Draw on the graphs to illustrate the changes in force and torque experienced by side A:

Quick Answers:

1a) 0.24 Nm     b) 0.48 Nm  

2a) 80 turns    b) clockwise


Worked Answers: