A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. In mechanically controlled variable capacitors, the distance between the plates or the amount of plate surface area which overlaps can be changed. Variable capacitors are mostly used in radio tuning circuits and they are sometimes called 'tuning capacitors'. Small variable capacitors operated by screwdriver are called trimmer capacitors.

Trimmer / Variable Capacitors