When two identical cells are connected either in series or in parallel across a $2 \ \Omega$ resistor,they send the same current through it. The internal resistance of each cell is: (in $\Omega$)

Two cells of equal $e.m.f.$ $E$ and internal resistances $r_1$ and $r_2$ $(r_1 > r_2)$ are connected in series. On connecting this combination to an external resistance $R$,it is observed that the potential difference across the first cell becomes zero. The value of $R$ will be

The $e.m.f.$ of a primary cell is $2 \ V$. When it is short-circuited,it gives a current of $4 \ A$. The internal resistance of the primary cell is ............. $\Omega$.

As shown in the figure,a group of $N$ cells is connected in series,where the $emf$ of each cell $E_n$ varies with its internal resistance $r_n$ according to the relation $E_n = 1.5 r_n$. The current $I$ in the circuit is ................ $A$.

The $n$ rows,each containing $m$ cells in series,are joined in parallel. Maximum current is drawn from this combination across 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:

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