Question

A wire of diameter 0.02 metre contains ${10}^{28}$ free electrons per cubic metre.For an electrical current of 100A, the drift velocity of the free electrons in the wire nearly.

• A. $1\times {10}^{-19}m/s$
• B. $5\times {10}^{-10}m/s$
• C. $2\times {10}^{-4}m/s$
• D. $8\times {10}^{3}m/s$

Answer 1

The correct option is C $2\times {10}^{-4}m/s$

We know $v_d=\frac{i}{neA}$

putting values

$v_d=\frac{100}{{10}^{28}\times 1.6\times {10}^{-19}\times \frac{\pi }{4}\times (0.02{)}^2}$

$=2\times {10}^{-4}m/sec$