Physics (AS & A Level) · Oct / Nov 2021 · Paper 11 · Question 32

The current $I$ in a wire is given 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 average drift velocity of the free electrons and $q$ is the charge of an electron. Which relationship is not used in the derivation of this equation?

1. Acharge = current × time
2. Bdistance = speed × time
3. Cnumber = number density × area
4. Dvolume = length × area

As printed in the paper