Question

The potential difference between the terminals of a cell is 20 V when a current of 2 A flows through the circuit. When the direction of current in the circuit is reversed, the potential difference between the terminals of the cell is 30 V. The internal resistance of the cell is

• A. 1 $\Omega$
• B. 1.5 $\Omega$
• C. 2 $\Omega$
• D. 2.5 $\Omega$

Hint:

Remember the two formulas for the terminal voltage of a cell: $V = \mathcal{E} - Ir$ for discharging (supplying current) and $V = \mathcal{E} + Ir$ for charging (receiving current from an external source). "Reversing the current" usually implies switching from discharging to charging.

Answer 1

The Correct Option is D