Question

If the resistivity of copper is `1.7 xx 10^(-6) Omega cm`, then the mobility of electrons in copper, if each atom of copper contributes one free electron for conduction, is [The amomic weight of copper is `63.54` and its density is `8.96 g//c c]` :
A. `23.36 cm^(2)//Vs`
B. `503.03cm^(2)//Vs`
C. `43.25 cm^(2)//Vs`
D. `88.0 cm^(2)//Vs`

Answer 1

Correct Answer - C
Mobility of electron `mu =(sigma)/(n e)-(1)`
also respectivity `rho = (1)/(sigma)`
From Eqs. (i) and (ii), we get `mu = (1)/(n e rho)`
Here, `n` = number of free electrons per unit volume
`n=(N_(0) xxd)/("atomicweight")`
`n=(6.023 xx10^(23) xx8.96)/(63.54) =8.5 xx 10^(22)`
From Eqs. (iii) and (iv), we get
`mu=(1)/(8.5 xx 10^(22) xx 1.6 xx 10^(-19) xx 1.7 xx 10^(-6))`
`:. mu=43.25 cm^(2)//Vs`.