Displacement current density
= Displacement current density
{title2=$\mathbf J_D=\partial_t\mathbf D$}
The time derivative of the <electric displacement field> enters the macroscopic <Ampère-Maxwell equation> alongside free <electric current density>. In vacuum, $\mathbf J_D=\epsilon_0\partial_t\mathbf E$. It is not transport of free charges through the vacuum gap of a <capacitor>; its <surface integral> nevertheless supplies the term needed for compatibility with the <continuity equation>.