An electric motor operating on a `50 V dc` supply draws a current of `12 A`. If the efficiency of the motor is `30 %`,estimate the resistance of the windings of the motor.

Explanation

Power drawn by motor is `P = VI = 50 xx 12 = 600 W`
Power loss `= ( 70)/(100) xx 600 = 420 W`
This power is lost in the form of heat in the resistance .
`I^(2) R = 420 or (12)^(2) R = 420 or R = 2.9 Omega`