The battery shown in the figure has an $e.m.f.$ $E$ and internal resistance $r$. The current in the circuit can be varied by sliding the contact $J$. If at any instant the current flowing through the circuit is $I$,the potential difference between the terminals of the cell is $V$,and the thermal power generated in the cell is equal to $\eta$ fraction of the total electrical power generated in it,then which of the following graphs is correct?

$A$ silver and zinc voltameter are connected in series and a current $i$ is passed through them for a time $t$ liberating $W \, g$ of zinc. The weight of silver deposited is nearly ..............$W$.

Statement $(I)$: The temperature coefficient of resistance for most metals in pure form is positive.
Statement $(II)$: $A$ metal wire $2 \ mm$ in diameter carries a charge of $360 \pi \ C$ in two hours. If the metal contains $5 \times 10^{22}$ free electrons $/ cm^3$, then the drift velocity of the electrons in the wire is $6.25 \times 10^{-6} \ m/s$.
Statement $(III)$: Semiconductors like pure germanium do not obey Ohm's law for all ranges of electric field values. Which of the following is correct?

$A$ cell having an emf $\varepsilon$ and internal resistance $r$ is connected across a variable external resistance $R$. As the resistance $R$ is increased,the plot of potential difference $V$ across $R$ is given by:

Two electric bulbs marked $25\ W - 220\ V$ and $100\ W - 220\ V$ are connected in series to a $440\ V$ supply. Which of the bulbs will fuse?

One junction of a certain thermoelectric couple is at a fixed temperature $T_r$ and the other junction is at temperature $T$. The thermo-electromotive force for this is expressed by $E=k(T-T_r)[T_0-\frac{1}{2}(T+T_r)]$. At temperature $T=\frac{1}{2} T_0$, the thermoelectric power is