Question

The terminal voltage of a cell is equal to

• A. potential across external resistance.
• B. potential across internal resistance.
• C. potential across sum of external resistance and internal resistance.
• D. emf of cell.

Answer 1

The correct option is A potential across external resistance.

Terminal voltage is the potential difference across the terminals of a load when the circuit is switched on. E.m.f is the maximum potential difference that can be delivered by a cell or a generator when no current flows through it.
Terminal voltage is measured by voltmeter whereas, E.m.f is measured by potentiometer.
Terminal voltage is always lesser than the emf of the cell. It is because of the drop in potential difference because of the current passing through the internal resistance of the cell or the generator.They are related by the equation $E=V+Ir$, where, $I$ is the current and r is internal resistance of the cell.