Key Concepts: Capacitance

Capacitors

• A capacitor stores electrical energy in an electric field between two conductors (plates).
• Capacitance: C = Q/V — the ratio of charge stored to voltage applied. Unit: Farad (F).

Parallel Plate Capacitor

• C = ε₀A/d, where A = plate area, d = plate separation, ε₀ = 8.85 × 10⁻¹² F/m.
• Inserting a dielectric material (κ) between plates increases capacitance: C = κε₀A/d.

Energy Stored

• E = ½CV² = ½QV = Q²/(2C).

Combinations

• Parallel: C_total = C₁ + C₂ + ... (add directly).
• Series: 1/C_total = 1/C₁ + 1/C₂ + ... (reciprocals add).