For en variabel kondensator med variabel kapacitans C (kondensatormikrofon) - og fastholdt lagret ladning Q gælder, at spændingen V spændingen varierer proportionalt med kapacitansen C:<ref>[http://www.audiomasterclass.com/newsletter/the-principle-of-operation-of-a-capacitor-condenser-microphone By David Mellor, Tuesday June 20, 2006, audiomasterclass.com: The principle of operation of a capacitor (condenser) microphone. A capacitor microphone works on the principle of Q=CV. If you don't know that, you should know that it's a good sound engineering interview question...], [https://web.archive.org/web/20180118203109/http://www.audiomasterclass.com/newsletter/the-principle-of-operation-of-a-capacitor-condenser-microphone backup]</ref>
:<math>V= \frac{Q}{C}</math>
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