JEE Main · 2021 · 27 Jul 2021 · Shift 1 · Current Electricity

Charge cannot pile up anywhere along the conductor, so the same current crosses every section and the electron current is unchanged from P to Q. Writing that current as $I=neA{v}_d$ with $n$ and $e$ fixed, the drift speed must rise where the area falls, and the area falls from $\pi r_1^2$ to $\pi r_2^2$. The field inside follows from $E=\frac{I}{\sigma A}$, which rises for the same reason. Moving from P to Q only the drift velocity of the electrons increases.