Question

When a galvanic cell is connected to an external volatge supply ($E_{ext}$), the electrons flow from cathode to anode because

Answer 1

The effect of opposing potential applied to galvanic cell as follows,

1. $E_{external}<\text{Electrical potential of cell}$
If an external opposing potential is lower than electrical potential of the cell, the normal reactions of the cell will occur and the electrons will flow from anode to cathode. Hence, the current
flows from cathode to anode.

2. $E_{external}=\text{Electrical potential of cell}$
When the external voltage is equal to the electrical potential of the cell, there will be no flow of electrons or current. Also, no chemical reaction.

3. $E_{external}>\text{Electrical potential of cell}$
If an external opposing potential is higher than electrical potential of the cell, the reaction begins to take place in the opposite direction i.e., non-spontaneous process starts.
Electron will flow from cathode to anode. Thus, current flow from anode to cathode.
Here, anodic ions begins to deposit on anode and cathode metal begins to deteriorate.