Question

A current $i$ is flowing through the wire of diameter $d$ having drift velocity of electrons $v_{d}$ in it. What will be new drift velocity when diameter of wire is made $d / 4$ ?

• A. $4 \,V_d$
• B. $\frac{V_{d}}{4}$
• C. $16\, V_d$
• D. $\frac{V_{d}}{16}$

Answer 1

Answer: (C)

I = nAeV_d
Now I is constant
$V_{d} \propto\frac{1}{A}$
If diameter of wire is $\frac{d}{4}$ then area is $\frac{1}{16}$
times so new drift velocity = 16 V_d