The insulating material between plates of a capacitor is called a __________.

• A. Dielectric
• B. Conductor
• C. Insulator
• D. Pyrolytic layer

Answer: (A)

The main idea is that the space between capacitor plates must be an insulating, polarizable material. This is called a dielectric. A dielectric prevents current flow like an insulator, but it can be polarized by the electric field between the plates, which helps store more charge for a given voltage. This polarization lowers the effective field inside the material and increases the capacitance, described by C = ε_r ε0 A / d, where ε_r is the dielectric constant of the material. A conductor would short the plates and ruin energy storage, so it’s not suitable. A generic insulator is too vague, whereas a dielectric specifically refers to the insulating, polarizable property that enables energy storage in the electric field. A pyrolytic layer is a specific material type and not the general term used for this purpose.