Question

Two identical cells, when connected either in parallel or in series gives same current in an external resistance $5 \Omega$ The internal resistance of each cell will be__ $\Omega$

Answer 1

The correct answer is 5.

i=5+2r2ε​…(1)
i=2r​+5ε​… (2)
Equating (1) and (2)
5+2r2ε​=2r​+5ε​
⇒r+10=5+2r
r=5