magnetic effects of electric current question bank for term 2

  A simple motor is made in a school laboratory. A coil of wire is mounted on an 

axle between the poles of a horseshoe magnet, as illustratedIn the example above, coil ABCD is horizontal and the battery is connected as 

shown. 

a. For this position, state the direction of the force on the arm AB.

b. Why does the current in the arm BC not contribute to the turning force on 

the coil?