Q. An electric motor operates on a $50\ volt$ supply and a current of $12A$. If the efficiency of the motor is 30%, what is the resistance of the winding of the motor
A) $6\Omega$
B) $4\Omega$
C) $2.9\Omega$
D) $3.1\Omega$
Explanation
(c) $\eta = \frac{e}{E} \times 100 \Rightarrow e = 0.3\ E$
Now, $i = \frac{E - e}{R} \Rightarrow 12 = \frac{50 - (0.3 \times 50)}{R} \Rightarrow R = 2.9\Omega$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.