A variable, opposite external potential $\left({\mathrm{E}}_{\mathrm{ext}}\right)$ is applied to the cell $\mathrm{Zn}\left|{\mathrm{Zn}}^{2+}\left(1\mathrm{M}\right)\parallel {\mathrm{Cu}}^{2+}\left(1\mathrm{M}\right)\right|\mathrm{Cu}$ of potential 1.1 V. When $E_{\text{ext }}<1.1\mathrm{V}$ and $E_{\text{ext }}>1.1\mathrm{V}$ respectively, electrons flow from:

The cell will function as a galvanic cell if ${\mathrm{E}}_{\mathrm{ext}}<1.1\mathrm{V}$,  at which point electrons will flow from the anode to the cathode.

${\mathrm{E}}_{\text{ext }}>1.1\mathrm{V},$ causes electrons to flow from cathode to anode, causing the cell to function as an electrolytic cell.