For a given temperature difference,which of the following pairs will generate maximum thermo $e.m.f.$?

For a thermocouple,the neutral temperature is $270\,^\circ C$ and the temperature of its cold junction is $20\,^\circ C$. If there is no deflection in the galvanometer,the temperature of the hot junction should be .............. $^\circ C$

The variation of current $(I)$ and voltage $(V)$ is as shown in figure $A$. The variation of power $P$ with current $I$ is best shown by which of the following graphs?

$A$ wire of length $L$ and $3$ identical cells of negligible internal resistances are connected in series. Due to current,the temperature of the wire is raised by $\Delta T$ in a time $t$. $A$ number $N$ of similar cells is now connected in series with a wire of the same material and cross-section but of length $2L$. The temperature of the wire is raised by the same amount $\Delta T$ in the same time $t$. The value of $N$ is

The Peltier coefficient for the junction of a pair of metals is proportional to:

$A$ $3\,^oC$ rise in temperature is observed in a conductor by passing a certain current. When the current is doubled,the rise in temperature will be ............. $^oC$.