Question

Three identical cells, each of emf $2V$ and unknown internal resistance are connected in parallel.This combination is connected to a $6\Omega$ resistor. The terminal potential difference across each cell is $1.5V$. What is the internal resistance of each cell?

Answer 1

Formula,

$V=\frac{ϵR}{r+R}$

Terminal voltage,

$V=\frac{ϵR}{\frac{r}{3}+R}$

$\Rightarrow 1.5=\frac{2\times 6}{\frac{r}{3}+6}$

$\therefore r=6\Omega$