The quantity kind \(\textit{Particle Current}\) can be used to describe the net number
of particles passing through a surface in an infinitesimal time interval.
\(\int J \cdot e_n dA = \frac{dN}{dt}\), where \(e_ndA\) is the vector surface element, \(N\) is the net number of particles passing over a surface, and \(dt\) describes the time interval.