Mobility

Mobility

 As we have seen, conductivity arises from mobile charge carriers.

 In metals, these mobile charge carriers are electrons; in an ionized gas, they are electrons and positive charged ions: in an electrolyte, these can be both positive and negative ions.

An important quantity is the mobility u defined as the magnitude of  the drift velocity per unit electric field:

The SI unit of mobility is m^2/vs and is 10^4 of the mobility in practical unit (cm^2/vs) . Mobility is positive 

where T is the average collision time for electrons.