Question

The back e.m.f. in a d.c. motor is maximum, when
(a) the motor has picked up max speed
(b) the motor has just started moving
(c) the speed of motor is still on the increase
(d) the motor has just been switched off

Answer 1

Answer:

(a) the motor has picked up max speed

Explanation:

The back emf depends, of course, on the speed of the motor- the change in magnetic flux that generates it increases with motor speed. So that as the motor begin to turn, the back emf grows until the motor has reached its maximum speed, at which point the back emf stays at its maximum value.

Answer 2

Answer:

sorry I didn't know this...