PHYSICS & ELECTRONICS / CAPACITORS / PAGE 34 OF 50
Capacitor Basics
Storing energy in an electric field.
A capacitor is two conductors separated by an insulator called the dielectric. Connect it to a voltage and charge builds up on the plates. Capacitance is the charge stored per volt, measured in farads, though real parts are usually microfarads or smaller.
Original diagram: capacitor basics
In a steady DC circuit a charged capacitor blocks current, while for AC it lets current flow, more easily at higher frequencies. For a parallel-plate capacitor, larger plates and a thinner gap give more capacitance.
- Energy stored = ½ C V².
- Reactance falls as frequency rises.
- Capacitors in parallel add their values.
KEY IDEA
C = Q / V and E = ½ C V²Browse all 50 physics and electronics pages | Back to the course index