Capacitors & Dielectrics

A capacitor stores electrical energy in the electric field between two conductors separated by a dielectric.

Capacitance C = Q/V, where Q is charge and V is potential difference. Unit: Farad (F).

For a parallel plate capacitor: C = ε₀κA/d, where A is plate area, d is separation, κ is dielectric constant.

Inserting a dielectric increases capacitance by factor κ. This is because the dielectric reduces the effective electric field.

Energy stored in a capacitor: U = ½CV² = ½QV = Q²/(2C).

In series combination: 1/C_eq = 1/C₁ + 1/C₂ + ... (charge same, voltage divides).

In parallel combination: C_eq = C₁ + C₂ + ... (voltage same, charge divides).

The electric field between plates is uniform: E = V/d = σ/ε₀ (for parallel plates without edge effects).