Question

For a cell, the terminal potential difference is 2.2 V when the circuit is open and reduces to 1.8 V, when the cell is connected across a resistance, $R=5\Omega$. The internal resistance of the cell is

• A. $\frac{10}{9}\Omega$
• B. $\frac{9}{10}\Omega$
• C. $\frac{11}{9}\Omega$
• D. $\frac{5}{9}\Omega$

Answer 1

The correct option is A $\frac{10}{9}\Omega$

In open circuit, E = V = 2.2 V, In close circuit, V = 1.8 V, $R=5\Omega$
So internal resistance, $r=(\frac{E}{V}-1)R=(\frac{2.2}{1.8}-1)\times 5\Rightarrow r=\frac{10}{9}\Omega$