Figure shows mixed grouping of identical cells each of $e.m.f. 4V$  and internal resistance $1\mathrm{\Omega }.$ This combination can be replaced by an equivalent cell between $A$ and $B$ having e.m.f. $E$ and internal resistance $r,$ where

The situation shown in figure is equivalent to

The potential difference between $A$ and $B$ in the following situation is

The equivalent resistance between $A$ and $B$ in the following figure is

In the circuit shown, the current drawn by the cell is

In the metre bridge experiment, the null point is obtained at $N.$ The value of unknown resistance $X$ will be

Which of the following materials obeys the nature of given voltage-current $(V-I)$ graph under constant temperature?

The equivalent resistance between the points A and B is