Variable capacitor is a type of capacitor whose capacitance can be adjusted within a certain range. When the effective area or distance between poles is changed, its capacitance will be changed accordingly. It is used as a tuning capacitor in radio receiving circuits. Generally, tunable capacitors with slotted screw type adjustments for making small adjustments in a circuit are called trimmers. The usual dielectric in these types of capacitors is ceramic or mica, and the capacitance value is usually changed by adjusting the distance of the plate. The capacitance of the trimmer capacitor is less than 100pF.
