variable capacitors

[dstcj]

Can anybody explain to me the function of a variable capacitor ?  

[ezapf]

     A capacitor charges when voltage is applied. It discharges when a load is applied. The larger the capacitor, the more charge it can hold and the slower it will discharge. A variable capacitor allows you to change the rate of charge and discharge.

     Capacitors are often used with inductors to create oscillators. By using a variable capacitor, you can change or fine-tune the frequency of the oscillator.

     Fairly large variable capacitors are often used with variable inductors as an impedance matching system between a radio transmitter and an antenna. This allows the same antenna to be used for a wide range of frequencies.

     Well, those are the basics and just a couple of examples. Hope this helps.

[romko]

commonly found in radio and TV IF circuits, car radio aerial trimmers etc.