Question

A copper wire has a cross-sectional area of 0.80 × 10-6 m2. The number density of electrons for copper is 9.5 × 10^28 m-3. A current of 18 A flows through the wire. Calculate the mean drift velocity of the free electrons in the wire. *

Answer 1

Answer: 1.480 mm/s

Explanation:

Given

Cross-sectional area $A=0.80\times 10^{-6}\ m^2$

Number density(no of charges per unit volume) $n=9.5\times 10^{28}\ m^{-3}$

Current $I=18\ A$

We know, drift velocity is given by

$\Rightarrow v_d=\dfrac{I}{neA}\\\Rightarrow v_d=\dfrac{18}{9.5\times 10^{28}\times 1.6\times 10^{-19}\times 0.8\times 10^{-6}}\\\Rightarrow v_d=\dfrac{18\times 10^{-3}}{12.16}=1.480\ mm/s$