Mercury cell consists of zinc – mercury amalgam as cathode.

In case two cells are identical, each of emf $E=5 \mathrm{V}$ and internal resistance $r=2 \Omega$, calculate the voltage across the external resistance $R=10 \Omega$

The circuit diagram of a potentiometer for determining the $\mathrm{emf} \text{'}\mathrm{E}\text{'}$ of a cell of negligible internal resistance is as shown in figure:

Derive an expression to find out internal resistance of a cell.

Two cells of emf $2E$ and $E$ with internal resistance $r_1$and $r_2$ respectively are connected in series to an external resistor $R$ (see figure). The value of $R,$ at which the potential difference across the terminals of the first cell becomes zero is

In the network shown, the equivalent resistance between $\mathrm{A}$ and $\mathrm{B}$ is $\frac{4}{3}\mathrm{\Omega }$, find the value of $\mathrm{r}$.

The figure shows a part of a closed circuit. If the current flowing through it is $2 \mathrm{A}$ then $V_B-V_A$ is _______

The variation of terminal potential difference $\left(V\right)$ with current flowing through as cell is as shown

The $\mathrm{emf}$ and internal resistance of the cell are