as level phyics 😮😮😮😮Watch
Kirchhoff's 2nd law has often been quite helpful for me - the sum of emfs supplied around each loop of a circuit is equal to the sum of potential differences across all components.
Total charge, Q=n*e*V so the amount of electrons n, with charge e, in a given volume V
I=(n*e*A*L)/t and as speed=dist/time.
I=n*e*a*v and then v=I/nae