Dielectrics, Capacitor Types and Uses

When a dielectric is placed between capacitor plates, its atoms or molecules become polarized. Bound positive and negative charges shift slightly in opposite directions. The dielectric's polarization creates an electric effect that opposes part of the original internal field. Under standard ideal conditions: C = κC₀ where: `κ` = relative permittivity or dielectric constant and: `C₀` = capacitance without dielectric. Common capacitor families include: ceramic; film; electrolytic; variable capacitors. Different types are chosen according to: capacitance range; voltage rating; stability; size; frequency behaviour; polarity requirements.

Capacitors are used for: temporary energy storage; filtering; smoothing; timing circuits; signal coupling; tuning and frequency selection.

**κ=C/C₀ C=κC₀ For fully filled parallel plates: C=κε₀A/d**