Question

A 2-ampere current flows in a conductor which has $1\times {10}^{24}$ free electrons per meter. What is their average drift velocity?

• A. $1.25m/s$
• B. $125000m/s$
• C. $3\times {10}^{8}m/s$
• D. $1.25\times {10}^{-5}m/s$

Answer 1

Answer: (A)

Step 1: Given that:

Electric current($I$) in the conductor= $2A$

Number of free electron in the conductor($n$) = $1\times {10}^{24}$

Area of cross section($A$) of the conductor= $1m^2$

Step 2: Calculation of average drift velocity of electrons:

The electric current is related to the drift velocity of the electron as;

$I=neA{v}_d$

Thus,

$2A=1\times {10}^{24}\times 1.6\times {10}^{-19}C\times 1m^2\times v_d$

$\Rightarrow 2=1.6\times {10}^5{v}_d$

$\Rightarrow v_d=\frac{2}{1.6\times {10}^5}$

$\Rightarrow v_d=1.25\times {10}^{-5}m{s}^{-1}$

Thus,

Option d) $1.25\times {10}^{-5}m{s}^{-1}$ is the correct option.