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

$A$ thermocouple is made of $Cu$ and $Fe$. If a battery is connected in it,then

One junction of a thermocouple is kept at a constant temperature $T_r$ and the other junction is kept at a temperature $T$. If the thermo-emf is given by $E = K(T - T_r) [T_0 - \frac{1}{2}(T + T_r)]$,what is the thermoelectric power at $T = \frac{1}{2}T_0$?

The thermo emf of a thermocouple is given by $E = aT + bT^2$,where $\frac{a}{b} = -200^{\circ}C$. If the cold junction is kept at $30^{\circ}C$,then the inversion temperature is ($\varepsilon$ in volt,$T$ in centigrade). (in $K$)

In the circuit shown here,the readings of the ammeter and voltmeter are

The temperature of the cold junction and the neutral temperature of a thermocouple are $15\,^{\circ}C$ and $280\,^{\circ}C$ respectively. The temperature of inversion is .............. $^{\circ}C$.