Question

$n$ identical cells, each of emf $\varepsilon$ and internal resistance $r$, are joined in series to form a closed circuit. The potential difference across any one cell is

• A. zero
• B. $\varepsilon$
• C. $\frac{\varepsilon}{n}$
• D. $\frac{n-1}{n} \varepsilon$

Answer 1

Answer: (A)

Current in circuit, is $i=\frac{n \varepsilon}{n r}=\frac{\varepsilon}{r}$

The equivalent circuit of one cell is shown in figure.
The potential difference across the cell is
$V_{A}-V_{B}=-\varepsilon+i r=-\varepsilon+\frac{\varepsilon}{r} r=0$