an electric motor operating on a 50v d.c supply draws a current of 12 a if the efficiency of the motor is 30% estimate the resistance of the winding motor.

Efficiency of motor is given by:

Efficiency = Input - losses/ Input

Input power = V*I = 50 * 12 = 600 Watt
Losses = Resistance losses = I2R losses = 122(R)= 144R 

0.3 = ‚Äč(600-144R) / 600 
180 = 600 -144R
144R= 420 
R = 2.91 ohms

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