The value of the internal resistance of an ideal cell is:

$n$ identical cells each of $e.m.f.$ $E$ and internal resistance $r$ are connected in series. An external resistance $R$ is connected in series to this combination. The current through $R$ is

Two cells of emfs $E_1$ and $E_2$ and internal resistances $r_1$ and $r_2$ ($E_2 > E_1$ and $r_2 > r_1$) respectively,are connected in parallel as shown in the figure. The equivalent emf of the combination is $E_{eq}$. Then

$n$ rows,each containing $m$ cells in series,are connected in parallel. The maximum current is drawn from this combination through an external resistance of $3\, \Omega$. If the total number of cells used is $24$ and the internal resistance of each cell is $0.5\, \Omega$,then $m$ and $n$ are respectively:

$A$ cell sends a current through a resistance $R$ for time $t$. Now the same cell sends current through another resistance $r$ for the same time. If the same amount of heat is developed in both the resistances,then the internal resistance of the cell is:

$A$ cell of $emf\;4\,V$ and internal resistance $0.5\,\Omega$ is connected to a $7.5\,\Omega$ external resistance. The terminal potential difference of the cell is $.....\,V$.