Find relation between `emf` and internal resistance of a cell.

A cell of emf E and internal resistance r drives a current of 5 Ampere through an extenal resistance of 8 ohm. The current drops to 4 Ampere when the external resistance is increased to 10.1 ohm. Find the emf E and the internal resistance r of the cell.

What do you mean by internal resistance of a cell?

Obtain a relation between Cv and the internal energy.