extend the conductivity expression in terms of mobility and explain how carrier concentration and mobility vary with respect to temperature?plz reply someone as soon as possible.....thanku.....

I suppose this question is from Semiconductors
See, for that we have I_Total = I_e + I_h
If { V is the potential difference across the semiconductor,

R is the resistance through the semiconductor,
e is the charge of electron and hole, 
N_e and N_h are the respective carrier densities,
A is the area of cross section of the semiconductor,
v_e and v_h are the drift velocities of electrons and holes respectively }
then, V/R = N_eeAv_e + N_heAv_h 
E.l / pl/A = eA.(N_ev_e + N_hv_h)
therefore, 1/p = e(N_ev_e/E + N_hv_h/E)
or 1/p = S = e(N_eu_e + N_hu_h)
where p is the resistivity, S is conductivity and u_e,u_h are respective mobilities.
As the temperature increases, the mobility of the carriers decrease upto certain extend but there is large increment in their concentrations. So there is a considerable increase in the conductivity of semiconductors wrt the conductivity expression.
Hope that’ll help.