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

Two wires '$A$' and '$B$' of the same material have their lengths in the ratio $1 : 2$ and radii in the ratio $2 : 1$. The two wires are connected in parallel across a battery. The ratio of the heat produced in '$A$' to the heat produced in '$B$' for the same time is

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

Answer the following questions:
$(a)$ $A$ steady current flows in a metallic conductor of non-uniform cross-section. Which of these quantities is constant along the conductor: current, current density, electric field, drift speed?
$(b)$ Is Ohm's law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm's law.
$(c)$ $A$ low voltage supply from which one needs high currents must have very low internal resistance. Why?
$(d)$ $A$ high tension $(HT)$ supply of, say, $6 \ kV$ must have a very large internal resistance. Why?

In steady state, a capacitor of capacitance $2 \mu F$ is charged to $4 \mu C$, as shown in the figure. If the internal resistance of the cell is $0.5 \Omega$, then the emf of the cell is (in $\text{V}$)

Assertion: In a simple battery circuit,the point of the lowest potential is the positive terminal of the battery.
Reason: The current flows towards the point of the higher potential,as it does in such a circuit from the negative to the positive terminal.