1.

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

Answer»

1 mm/s
2 mm/s
0.5 mm/s
0.36 mm/s

Solution :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`


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