Electric Current, Resistance & D.C. Circuits

Charge and current

Electric current is the rate of flow of charge: $I = \dfrac{\Delta Q}{\Delta t}$, so $Q = It$. Current is measured in amperes; charge in coulombs. The charge on an electron is $e = 1.60\times10^{-19}\ \text{C}$. For charge carriers of number density $n$, cross-section $A$ and drift velocity $v$: $I = nAve$.