A variable capacitor's performance is dependent on what factor?

The performance of a variable capacitor is primarily dependent on the adjustable plate separation. A variable capacitor operates by changing the distance between its plates, which in turn affects the capacitance. Capacitance is defined by the formula:

[ C = \frac{\varepsilon A}{d} ]

where ( C ) is the capacitance, ( \varepsilon ) is the permittivity of the dielectric, ( A ) is the area of the plates, and ( d ) is the separation between the plates. By being able to adjust the plate separation, this type of capacitor allows for a change in capacitance, making it versatile for tuning applications in circuits, such as radio frequency circuits where precise capacitance values are needed for tuning frequencies.

Other factors, like the type of dielectric used, do play a role in determining the basic characteristics and limits of the capacitor, but the key feature of variable capacitors that allows them to vary capacitance during operation is indeed the adjustable plate separation. The voltage applied affects dielectric breakdown and the electric field but does not influence the variable nature of the capacitance itself. The size of the capacitor can relate to its overall capacitance value, but again, it is not the variable element in a variable