Estimate the average drift speed of conduction electrons in a copper wire of cross sectional area `1 times 10^-7 m^2` carrying a current of 1.5 A.Assume that each copper atom contributes one conduction electron. The density of copper is `9 times 10^3 kg.m^-3` and its atomic mass is `63.5 u`.

Explanation

We know drift velocity
`v_d=1/(n eA)`..........(1)
Here I=1.5 A ,e=`1.6 times 10^19 C,A=1 times 10^-7 m^2`
and n= number of electrons per unit volume
Now, number of atoms per unit volume of copper
`n'=N/Mrho=(6times10^26times9times10^3)/63.5=8.5times10^28m^-3`
`therefore` One atom of copper contributes one conduction electron, therefore number density of electrons
`n=n'=8.5times10^28m^-3`
Using the values of n,e and A in equation (1) , we get
`v_d=1.5/(8.5times10^28times1.6times10^-19times1times10^-7)`
`=1.1times10^-3m.s^-1`