Q. Under what condition will the strength of current in a wire of resistance $R$ be the same for connection is $n$ series or in parallel of $n$ identical cells each of the internal resistance $r$, when
A) $R = nr$
B) $R = r/n$
C) $R = r$
D) $R \rightarrow \infty,r \rightarrow 0$
Explanation
(c) In series combination of cells current, $i = \frac{nE}{nr + R}$
In parallel combination of cell, $i^{'} = \frac{E}{(\frac{r}{n) + R}}$
If $i = i^{'}\ then\ \frac{nE}{nr + R} = \frac{E}{(\frac{r}{n) + R}} = \frac{nE}{r + nR}$
It will be so if $r = R$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.