Electrostatic Potential & Capacitance
Class 12 · Electrostatic Potential & Capacitance

Variable (Air-Gang) Capacitor

C ∝ |cosθ|. Rotate the shaft to tune from radio receiver-style sweep.

Run simulation

Key Notes

01

Multi-vane gang capacitor: capacitance varies as overlap area changes.

02

C(θ) ∝ |cosθ| for half-circle vanes — used in tuned LC radio receivers.

03

Allows manual tuning of resonant frequency f₀ = 1/(2π√(LC)).

Formulas

Variable C

N stator+rotor plates.

Important Points

Found in vintage AM radios — turning the dial rotates the rotor.

Replaced by varactor diodes in modern electronics.

Variable (Air-Gang) Capacitor notes from sciphylab (also known as SciPhy, SciPhy Lab, SciPhy Labs, Physics Lab). Class 12 physics revision for JEE Mains, JEE Advanced, NEET UG, AP Physics 1/2/C, SAT, and CUET-UG.