The underlying differential equation for this very minimal model is a non-dimensional version of the equation for an RC circuit, with charge measured in units of C*emf, and time measured in units of RC.

The underlying differential equation for this very minimal model is a non-dimensional version of the equation for an RC circuit, with charge measured in units of C*emf, and time measured in units of RC.

A simple model of a capacitor being charged. The instantaneous charge grows at a rate equal to the difference between it and the final charge, given as CV, divided by a time constant, which can set with a slider.