Question

At room temperature, copper has free electron density of $8.4 \, \times \, 10^{28} \, m^{- 3}$ . The electron drift velocity in a copper conductor of cross-sectional area $10^{- 6} \, m^{2}$ and carrying a current of $5.4 \, A$ , will be -

• A. $4 \, m \, s^{- 1}$
• B. $0.4 \, m \, s^{- 1}$
• C. $4 \, c m \, s^{- 1}$
• D. $0.4 \, m m \, s^{- 1}$

Answer 1

Answer: (D)

Use $i=ne \, A v_{d}$
$\therefore \, v_{d}=\frac{i}{n e A}$
$v_{d} = \frac{5.4}{8.4 \times 10^{28} \times 1.6 \times 10^{- 19} \times 10^{- 6}}$
$v_{d} = \frac{5.4 \times 10^{- 3}}{8.4 \times 1.6}$
$v_{d} = 0.4 \, \, m m \, \, s^{- 1}$