First a set of n equal resistors of R

CBSE Class 12 CBSE Class 12 Physics
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1

First a set of n equal resistors of R each are connected in series to a battery of emf E and internal resistance R and current I is observed to flow. Then, the resistors are connected in parallel to the same battery.It is observed that the current is increased 10 times. What is n?

2

In series combination of resistors, current I is given by
I = E/E + nR
Whereas, in parallel combination current 10 I is given by

E/R + R/n = 10 I
====> E/R+R/n = 10 (E/R+nR)
Now, according to problem, 1+n/1+1/n =10
===>10 = (1+n/n+1)n
===> n = 10