The direction of current in an iron-copper thermocouple is

$A$ metallic conductor of irregular cross-section is as shown in the figure. $A$ constant potential difference is applied across the ends $(1)$ and $(2)$. Then:

The net current flowing in the given circuit is . . . . . . $\text{A}$.

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

Total $emf$ produced in a thermocouple does not depend on

$A$ 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: