There's also a phenomenon known as Dielectric Absorption, where capacitors partially recharge from energy that was temporarily absorbed by their dielectric materials. The mil-spec test for it involves charging with a certain voltage, for a certain length of time, disconnecting them for a certain length of time, and then measuring their voltage. But that's just the test. They also exhibit the associated behavior while in use. That's why, for certain types of circuits, it's very important to use capacitors with a low dielectric absorption specification. Teflon, polystyrene, and polypropylene film dielectrics are among the best, in that regard.
- Tom Gootee
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