The capacitor (or condenser) accumulates opposite electrical charges on its plates. The device on display, named after the German physicist Ulrich Theodor Aepinus (1724 – 1802), serves in particular to demonstrate that the accumulated charge decreases as the distance between the plates increases.

The capacitor is composed of two circular brass plates supported by glass bars coated with sealing wax, fixed to two wooden supports (painted black). One of the two supports is hinged and allows the plates to be tilted from the vertical; it can also be slid in a slot in the base, so as to vary the distance between the plates.

Device on display.