Question

The potential difference in open circuit for a cell is $2.2V$. When a $4\Omega$ resistor is connected between its two electrodes the potential difference becomes $2V$. The internal resistance of the cell will be

• A. $1\Omega$
• B. $0.2\Omega$
• C. $2.5\Omega$
• D. $0.4\Omega$

Answer 1

The correct option is D $0.4\Omega$

Given : $E=2.2$ volts, $V=2$ volts and $R=4\Omega$

Internal resistance of the cell
$r=\frac{E-V}{V}R=\frac{2.2-2}{2}\times 4\Omega =0.4\Omega$