Electro Magnetic Induction And Alternating Currents Question 237
Question: An electric motor operating on a 60 V dc supply draws a current of 10 A. If the efficiency of the motor is 50%, the resistance of its winding is [AMU (Engg.) 2001]
Options:
A) $ 3\Omega $
B) $ 6\Omega $
C) $ 15\Omega $
D) $ 30\Omega $
Show Answer
Answer:
Correct Answer: A
Solution:
Efficiency $ \eta =50%\ $ So $ e=E/2 $
and $ i=\frac{E-e}{R}\Rightarrow i=\frac{E-E/2}{R}=\frac{E}{2R} $
$ \Rightarrow R=\frac{E}{2i}=\frac{60}{2\times 10}=3\Omega $
