Question

A current of $10A$ is maintained in a conductor of cross-section $1c{m}^2$. If the number density of free electrons be $9\times {10}^{28}{m}^{-3}$, the drift velocity of free electrons is

• A. $6.94\times {10}^{-6}$m/s
• B. $5.94\times {10}^{-2}$m/s
• C. $1.94\times {10}^{-3}$m/s
• D. $2.94\times {10}^{-4}$m/s

Answer 1

The correct option is C $1.94\times {10}^{-3}$m/s

The relation between current and drift velocity

$I.e1=V_d.e.n.a$

where $I=$ current

$V_d=$ current velocity

$e=$ electron

$n=$ no. of electrons per unit volume

$a=$ area of cross section

Now, $V_d=\frac{I}{nea}$

$=\frac{10}{1\times {10}^{-4}\times 9\times {10}^7\times 28}=1.94\times {10}^{-3}m/s$