<P> Current density is a measure of the density of an electric current . It is defined as a vector whose magnitude is the electric current per cross-sectional area . In SI units, the current density is measured in amperes per square metre . </P> <Dl> <Dd> I = ∫ J → ⋅ d A → (\ displaystyle I = \ int (\ vec (J)) \ cdot d (\ vec (A))) </Dd> </Dl> <Dd> I = ∫ J → ⋅ d A → (\ displaystyle I = \ int (\ vec (J)) \ cdot d (\ vec (A))) </Dd> <P> where I (\ displaystyle I) is current in the conductor, J → (\ displaystyle (\ vec (J))) is the current density, and d A → (\ displaystyle d (\ vec (A))) is the differential cross-sectional area vector . </P>

Relationship between potential difference and direction of flow of current in an electric circuit