Q. The number of dry cells, each of e.m.f. $1.5\ volt$ and internal resistance $0.5\ ohm$ that must be joined in series with a resistance of $20\ ohm$ so as to send a current of $0.6\ ampere$ through the circuit is
A) 2
B) 8
C) 10
D) 12
Explanation
(c) In series $i = \frac{nE}{nr + R} \Rightarrow 0.6 = \frac{n \times 1.5}{n \times 0.5 \times 20} \Rightarrow n = 10$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.