Displacement current The physicist James Clerk Maxwell invented the concept of displacement current dD dt to make Amp re s law consistent with conservation of charge in cases where charge is accumulating as in a capacitor He interpreted this as a real motion of charges even in vacuum where he supposed that it corresponded to motion of dipole charges in the aether Although this interpretation has been abandoned Maxwell s correction to Amp re s law remains valid Hydraulic analogy As electrical circuitry can be modeled by fluid flow a capacitor can be modeled as a chamber with a flexible diaphragm separating the input from the output As can be determined intuitively as well as mathematically this provides the correct characteristics The pressure difference voltage difference across the unit is proportional to the integral of the flow current A steady state current can not pass through it because the pressure will build up across the diaphragm until it equally opposes the source pressure but a transient pulse or alternating current can be transmitted An overpressure results in bursting of the diaphragm analogous to dielectric breakdown The capacitance of units connected in parallel is equivalent to the sum of their individual capacitances