Two identical cells give the same current through an external resistance of $2 \Omega$ regardless of whether the cells are connected in series or in parallel. The internal resistance of each cell is: (in $\Omega$)

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

Two cells of $emfs$ $E_1$ and $E_2$ and internal resistances $r_1$ and $r_2$ are connected in parallel. The $emf$ and internal resistance of the equivalent source is

Two batteries of different emfs and different internal resistances are connected as shown. The voltage across $AB$ in volts is

Two cells $E_1$ and $E_2$ having equal $EMF$ $E$ and internal resistances $r_1$ and $r_2$ $(r_1 > r_2)$ respectively are connected in series. This combination is connected to an external resistance $R$. It is observed that the potential difference across the cell $E_1$ becomes zero. The value of $R$ will be

$A$ battery of $24$ cells,each of emf $1.5\,V$ and internal resistance $2\,\Omega$,is to be connected in order to send the maximum current through a $12\,\Omega$ resistor. The correct arrangement of cells will be: