What will be the internal resistance of a cell of emf 2.2 V which gives a current of 0.2 A through a resistance of 10 \( \Omega \)?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 1.0\,\Omega \)
The current through a cell of emf \( \varepsilon \) and internal resistance \( r \) connected to an external resistance \( R \) is
\( \displaystyle I = \frac{\varepsilon}{R + r} \;\Rightarrow\; r = \frac{\varepsilon}{I} - R \)
\( \displaystyle r = \frac{2.2}{0.2} - 10 = 11 - 10 = 1.0\,\Omega \)