Q. The armature of a shunt wound motor can with stand current up to 8A before it overheats and it damaged. If the armature resistance is 0.5 $\Omega$, minimum back emf that must be motor is connected to a 120 V line is
A) 120 V
B) 116 V
C) 124 V
D) 4 V
Explanation
(b) From $R = \frac{E - V}{i}$
$0.5 = \ \frac{120 - V}{8}$
$V\ = 116\ V$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.