Drift velocity of electrons in a wire of a certain length and the circular cross-section is, $V_{d.}$. The potential difference across the wire and the wire length is doubled but, the radius of the cross-section is halved. What is the new drift speed?

Assertion :- Resistivity of metals decreases with decrease in temperature but have some finite value as the temperature approaches absolute zero.

Reason :- The residual resistivity near absolute zero is caused primarily by the collision of electrons with impurities and imperfections in the metal.

If a wire is stretched to make it $0.2\%$ longer, its resistance will be