Question

A potential difference V is applied across a copper wire of diameter d and length L. when only d is doubled, the drift velocity :-

• A. increases two times
• B. decreases $\frac{1}{2}$ times
• C. does not change
• D. decreases $\frac{1}{4}$ times

Answer 1

The correct option is C does not change

Drift velocity $v_d=\frac{I}{neA}=\frac{V/R}{neA}=\frac{V}{neA\left(\frac{\rho L}{A}\right)}=\frac{V}{ne\rho L}$
Thus, drift velocity is independent of diameter so it does not change.