Two cells with the same e.m.f. $E$ and different internal resistances $r_1$ and $r_2$ are connected in series to an external resistance $R$. The value of $R$ so that the potential difference across the first cell is zero is

Thousand cells of same emf $E$ and same internal resistance $r$ are connected in series in the same order without an external resistance. The potential drop across $399$ cells is found to be ......... $E$.

Consider a parallel combination of the cells shown in the figure. The potential difference between $B_1$ and $B_2$ is

The potential difference between the terminals of a cell is $20 \ V$ when a current of $2 \ A$ flows through the circuit. When the direction of current in the circuit is reversed,the potential difference between the terminals of the cell is $30 \ V$. The internal resistance of the cell is (in $\Omega$)

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

For an open circuit condition,what is the value of the terminal voltage of a cell?