Current is flowing with a current density `J=480Acm^(-2)` in a copper wire. Assuming that each copper atom contributes one free electron and given that
Avogadro number = `6.0xx10^(23)` atoms/mole
Density of copper = `9.0g//cm^(3)`
Atomic weight of copper = 64 g/mole
Electronic charge `=1.6xx10^(-19)` coulomb
The drift velocity of electrons is

Options

A. 1 mm/s
B. 2 mm/s
C. 0.5 mm/s
D. 0.36 mm/s

Answer

D

Explanation

Drift velocity, `v_(d)=("Current density")/(n e)`
n = number of electrons per unit volume
or `n=(("Avogadro number")xx"Density")/("Atomic weight of copper")`
or `n=(6xx10^(23)xx9)/(64)`
`v_(d)=480xx(64)/(6xx10^(23)xx9xx1.6xx10^(-19))=(480xx64)/(6xx9xx1.6xx10000)cm//s`
`or v_(d)=(32)/(900)cm//s=(32xx10)/(900)mm//s=0.36 mm//s`