Question

If the free electron density of copper is `8.6xx10^(28)m^(-3)` and resistivity of copper at room temperature is `1.7xx10^(-6)Omega cm`, find the relaxation time for the free electrons of copper. Given, mass of electron `=9.1xx10^(-31) kg` , and charge of electron `=1.6xx10^(-19)C`.

Answer 1

Here, `m=8.6xx10^(28) m^(-3)`,
`rho =1.7xx10^(-6)Omega cm=1.7xx10^(-8)Omega m`,
`m=9.1 xx10^(-31) kg, e=1.6xx10^(-19)`
As `rho= m/("ne"^(2) tau)` so `tau=m/("ne"^(2) rho)`
`:. tau =(9.1xx10^(-31))/((8.6xx10^(28))xx(1.6xx10^(-19))^(2)xx(1.7 xx10^(-8))`
`=2.43 xx10^(-14)s`