A rotating electric motor also develops an induced emf; this is called a "back emf".
The current through a rotating electric motor is greatly reduced because of its "back emf".
The current through a non-rotating electric motor may be great enough to damage the motor.
While the motor is running, the net potential difference is
Vnet = Vext - E = 12 V - 9 V = 3 V
so the current is
I = V/R = 3/6 = 0.5 A
However, . . .
While the motor is stopped the net potential difference is
Vnet = Vext = 12 V - 0 = 12 V
so the current is now
I = V/R = 12/6 = 2.0 A !!!!!
(c) Doug Davis, 2003; all rights reserved
Return to Ch 21, Electromagnetic Induction