Question

A copper wire with a cross-section area of $2 \times 10^{-6} \, m^2$ has a free electron density equal to $5 \times 10^{22} /cm^{-3}$. If this wire carries a current of $16\,A$, the drift velocity of the electron is

• A. 1 m/s
• B. 0.1 m/s
• C. 0.01 m/s
• D. 0.001 m/s

Answer 1

Answer: (D)

0.001 m/s

Answer 2

Drift velocity, $V_{d}=\frac{I}{n e A}$
Given, $=n=5 \times 10^{22} / cm ^{3}$
$=5 \times 10^{22} \times 10^{6} / m ^{3}$
$e=1.6 \times 10^{-19} C$
$A=2 \times 10^{6} m ^{2}$
$I=16\, A$
$V_{d}=\frac{16}{5 \times 10^{28} \times 1.6 \times 10^{-19} \times 2 \times 10^{-6}}$
$=\frac{1}{10^{3}}=0.001 \,m / s$