A current $i$ passes through a metal wire of length $l$, radius of cross-section $r$ and conductivity $\sigma$. The rate of heat generation is

The equivalent resistance between $A$ and $B$ in the situation shown is

In the situation shown, the potential difference across the cell of smaller e.m.f. is

In the situation shown, the currents through $3\Omega$ and $2\Omega$ resistances are in the ratio

Figure shows mixed grouping of identical cells each of e.m.f. $4 \mathrm{V}$ and internal resistance $1\Omega$. 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