A cell with electromotive force $E$ and internal resistance $r$ is joined to an external resistor, as illustrated. The circuit current is $I$ and the potential difference (p.d.) across the external resistor is $V$. In the relationship $(E - V) = Ir$, what quantity is represented by $(E - V)$?
- Aelectrical energy per unit charge lost in the cell
- Belectrical energy per unit charge lost in the complete circuit
- Celectrical energy per unit charge lost in the connecting wire
- Delectrical energy per unit charge lost in the external resistor