If the potential difference across the terminals of a cell is greater than its emf, then
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → the cell is being charged
The terminal voltage of a cell depends on the direction of the current through it.
\( \text{Discharging (current leaves the positive terminal): } V = E - Ir \lt E \)
\( \text{Charging (current driven into the positive terminal): } V = E + Ir \gt E \)
So \( V \gt E \) only while an external source drives current into the cell against its emf, that is, while it is being charged.
Why the other options are incorrect
Option (2) the cell is in an open circuit. — Incorrect. In an open circuit no current flows, so V = E exactly.
Option (3) the cell is being discharged — Incorrect. While the cell is discharging, V = E − Ir, which is less than E.
Option (4) the internal resistance of the cell is zero — Incorrect. With zero internal resistance the terminal voltage equals E for any current; it cannot exceed E.