Mobility’s of electron and hole in a sample of Ge at room temperature are $0.36m^2/V-sec$ and $0.17m^2/V-sec$ respectively. If electron and hole densities are equal and it is $2.5 ×10^{13}/cm^3$

Data :- $μ_e = 0.36 m^2/V-sec $

$ μ_h = 0.17m^2/V-sec$ T =300°K

$n_i=2.5×10^{13}/cm^3 = 2.5×10^{19} m^3$

Formula :- $ σ=n(μ_e- μ_h ).e$

Calculations :- $σ=2.5×10^{19} (0.36+0.17)×1.6×10^{(-19)}$

=2.12 mho/metre

Answer :- σ= conductivity = 2.12 mho/metre