The current $I$ in a wire is expressed by the equation $I = nAvq$ where $n$ is the number density of the free electrons, $A$ is the cross-sectional area of the wire, $v$ is the mean drift velocity of the free electrons and $q$ is the charge on an electron. Which relationship is not involved in deriving this equation?
- Acharge = current \times time
- Bdistance = speed \times time
- Cnumber = number density \times area
- Dvolume = length \times area