Spark image
Back emf in a motor


As soon as the coil in the motor starts rotating, a back e.m.f. will be induced in it, and this will tend to reduce the current through it. For a supply e.m.f. E (say 60V), a back e.m.f. e and a coil of resistance R the current through the coil I will be:
I = [E e]/R

The faster the motor rotates the greater the back e.m.f.
 
 
 
© Keith Gibbs 2011