Which of the following represents a $volt$?

$A$ battery consists of a variable number $n$ of identical cells (each having electromotive force $\varepsilon$ and internal resistance $r$) which are connected in series. The terminals of the battery are short-circuited and the current $I$ is measured. Which of the graphs shows the correct relationship between $I$ and $n\,?$

In the Seebeck series,$Sb$ appears before $Bi$. In an $Sb-Bi$ thermocouple,the current flows from:

$A$ battery of $emf$ $E$ is being charged from a charger such that the positive terminal of the battery is connected to terminal $A$ of the charger and the negative terminal of the battery is connected to terminal $B$ of the charger. The internal resistance of the battery is $r$.

$A$ coil of wire of resistance $50\,\Omega$ is embedded in a block of ice. If a potential difference of $210\,V$ is applied across the coil,the amount of ice melted per second will be

Two heaters $A$ and $B$ have power ratings of $1 \text{ kW}$ and $2 \text{ kW}$,respectively. These two are first connected in series and then in parallel to a fixed power source. The ratio of power outputs for these two cases is: