Question

A wire of diameter $0.02 m$ contains $10^{28}$ free electrons per cubic metre. An electrical current of 100 flows through the wire. The drift velocity of the free electrons in the wires is nearly

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

Answer 1

Answer: (C)

By using $V_{d}=\frac{I}{n e A}$
$=\frac{100}{10^{28} \times 1.6 \times 10^{-19} \times \frac{\pi}{4} \times(0.02)^{2}}$
$=\frac{10^{2}}{10^{9} \times 0.4 \times 3.14 \times 0.0004}$
$V _{ d }=2 \times 10^{-4} m / s$