Question

What will produce a back emf in an electrical circuit?

Answer 1

The induced emf acts in opposite direction to the applied voltage V ( According to Lentz law) and it is known as back emf. Back emf is propotional to the motor angular velocity.

The presence of back emf makes the d.c. motor a self-regulating machine i.e., it makes the motor to draw as much armature current as is just sufficient to develop the torque required by the load. ie that back emf in a d.c. motor regulates the flow of armature current i.e., it automatically changes the armature current to meet the load requirement.