A solid conductor has a cross-section area $1 {\mathrm{cm}}^2$ and $2 {\mathrm{cm}}^2$, as shown in the figure. A current of $20 \mathrm{A}$ enters at $A$. Then

A potentiometer wire $PQ$ of $1 \mathrm{m}$ length is connected to a standard cell $E_1$. Another cell $E_2$ of emf $1.02 \mathrm{V}$ is connected with a resistance $r$ and switch $S$ (as shown in figure). With switch $S$ open, the null position is obtained at a distance of $49 \mathrm{cm}$ from $\mathrm{Q}$. The potential gradient in the potentiometer wire is :

In the given figure, there is a circuit of potentiometer of length $AB=10 \mathrm{m}$. The resistance per unit length is $0.1 \mathrm{\Omega }$ per $\mathrm{cm}$. Across $AB$, a battery of emf $E$ and internal resistance $r$ is connected. The maximum value of emf measured by this potentiometer is:

The value of current $I$ as shown in the given circuit diagram is