Dielectric
Definition
An insulating material placed between capacitor plates that boosts how much charge the capacitor can store.
Symbol: · Unit: dimensionless
Technical definition
A non-conducting material characterized by relative permittivity εᵣ (dielectric constant). Inserting it increases capacitance by factor εᵣ (C = εᵣC₀) by polarizing and partially canceling the internal field. It also raises the breakdown voltage.
Example
Paper (εᵣ ≈ 3.7) or ceramic (εᵣ up to thousands) between plates multiplies a capacitor's storage several-fold compared to air.
Common confusion
A dielectric does not conduct — it polarizes. Its molecules shift slightly to oppose the field, which is precisely why capacitance increases. Confusing it with a conductor gets the physics backwards.