Two identical cells, when connected either in parallel or in series gives same current in an external resistance $$5 ~\Omega$$. The internal resistance of each cell will be ___________ $$\Omega$$.

If the potential difference between $\mathrm{B}$ and $\mathrm{D}$ is zero, the value of $x$ is $\frac{1}{n} \Omega$. The value of $n$ is __________.

In the following circuit, the magnitude of current I₁, is ___________ A.

A null point is found at 200 cm in potentiometer when cell in secondary circuit is shunted by 5$$\Omega$$. When a resistance of 15$$\Omega$$ is used for shunting, null point moves to 300 cm. The internal resistance of the cell is ___________$$\Omega$$.