Variable air capacitor

Definition

A variable air capacitor is a type of capacitor where the capacitance can be adjusted by changing the overlapping area or distance between its plates, with air as the dielectric medium. It is commonly used in tuning circuits and radio frequency applications.

5 Must Know Facts For Your Next Test

1. The capacitance of a variable air capacitor is typically adjusted by rotating a set of movable plates relative to a set of fixed plates.
2. Air serves as the dielectric material, which means it has a very low dielectric constant (close to 1).
3. Variable air capacitors are often used in LC (inductor-capacitor) circuits for tuning radios and other RF (radio frequency) devices.
4. The capacitance range for these capacitors typically spans from a few picofarads (pF) to several hundred picofarads.
5. The quality factor (Q-factor) of variable air capacitors is generally high because air has low dielectric losses.

Review Questions

• How does changing the position of the plates in a variable air capacitor affect its capacitance?
• What role does air play in the operation of a variable air capacitor?
• In what types of applications are variable air capacitors most commonly used?

Related terms

Capacitance: The ability of a system to store an electric charge, measured in farads (F).

Dielectric Material: An insulating material placed between the plates of a capacitor that affects its capacitance.

Quality Factor (Q-Factor): \text{A dimensionless parameter that describes how underdamped an oscillator or resonator is, indicating its efficiency.}