Question

An Electric Motor operating on a 30V supply draws a current of 10A and yields mechanical power of 120W. Calculate:-

1) the efficiency of the motor.

2) the resistance of the winding of the motor

Answer 1

Given V =30 V, I =10 A and output power = 120 W.
(1) Electric power consumed by motor (input power)= VI = 300 W
Therefore efficiency of motor =$\frac{outputpower}{inputpower}\times 100=\frac{120}{300}\times 100=40\%$.
(2) As we know , $R=\frac{V}{I}$
Thus resistance of coil=$\frac{30}{10}\Omega =3\Omega$