Two cells,each of $e.m.f.$ $E$ and internal resistance $r$,are connected in parallel across an external resistor $R$. The maximum energy delivered to the resistor occurs when:

The terminal potential difference of a cell is greater than its $e.m.f.$ when it is

When an external resistance of $5\text{ }\Omega$ is connected across the terminals of a cell,a current of $0.25\text{ A}$ flows through it. When the $5\text{ }\Omega$ resistor is replaced by a $2\text{ }\Omega$ resistor,a current of $0.5\text{ A}$ flows through it. The internal resistance of the cell is . . . . . . $\Omega$.

When cells are connected in parallel,then

The potential difference in open circuit for a cell is $2.2\, V$. When a $4\, \Omega$ resistor is connected between its two electrodes,the potential difference becomes $2\, V$. The internal resistance of the cell will be .............. $\Omega$.

Electromotive force is the force,which is able to maintain a constant