A wire of uniform cross-section and length $l$ has a resistance of $16\Omega$. It is cut into four equal parts. Each part is stretched uniformly to length / and all the four stretched parts are connected in parallel. Calculate the total resistance of this combination.

The figure shows the variation of potential difference $V$ with length $l$ of the wire for two potentiometers $X$ and $Y$. Which one will you prefer for comparing emfs of two cells and why?

A part of an electric circuit is shown in the figure below :

Using Kirchhoff's $2\mathrm{nd}$ law, find the current $I$ flowing through the $4\Omega$ resistor.