A galvanic cell behaves as electrolytic cell when?

$E_{ext} > E_{cell}$

The correct answer is Option (3) → $E_{ext} > E_{cell}$

A galvanic cell is forced to behave as an electrolytic cell when an external voltage ($E_{\text{ext}}$) is applied that is large enough to overcome its inherent voltage and drive the reaction in the reverse, non-spontaneous direction.

The conditions governing the cell's behavior are:

1. $E_{\text{cell}} > E_{\text{ext}}$ (or $E_{\text{ext}} < E_{\text{cell}}$): The cell continues to operate as a Galvanic Cell, producing current because its spontaneous potential is greater than the opposing external potential.
2. $E_{\text{cell}} = E_{\text{ext}}$: The cell is at Equilibrium, and no current flows through the circuit.
3. $E_{\text{ext}} > E_{\text{cell}}$: The external voltage is now the dominant force. It drives the non-spontaneous reaction (the reverse of the galvanic reaction), converting electrical energy into chemical energy. The cell now acts as an Electrolytic Cell. This is the principle used in charging rechargeable batteries (like the lead storage cell).

The correct answer is: $E_{\text{ext}} > E_{\text{cell}}$