Question

A potential difference of V is applied at the ends of a copper wire of length $l$ and diameter $d$. On doubling only the length, the drift velocity:

• A. Becomes twice.
• B. Becomes half.
• C. Does not change.
• D. Becomes one fourth.

Answer 1

The correct option is C Does not change.

Drift velocity of an electron is given by
$v_d=\frac{i}{neA}$,
where n is the no. of electrons present per $m^3$ of the conductor, $e$ is the electron charge and $A$ is the cross-sectional area of the conductor.
So, it is obvious that the drift velocity doesn’t depend upon the length of the conductor.