Vacuum capacitor

The types of capacitors differ mainly in the dielectric used - the insulating material between the two electrodes. The dielectric affects the capacity to size ratio and also the electric losses and maximal voltage. The materials that provide good capacity to size ratio have big losses or low maximal voltage, so the choice of the proper material is always a compromise. If the size and price does not matter and low losses and high voltage endurance are important, vacuum is the best choice. The losses of the vacuum are zero, but the capacity to size ratio is the worst possible. Vacuum capacitors were used in transmitters, radars and similar devices.