What term describes the insulating material between capacitor plates?

• A. Dielectric
• B. Insulation
• C. Air gap
• D. Dielectric material

Answer: (A)

Dielectric is the term for the insulating, polarizable material placed between capacitor plates. It prevents direct current flow while allowing the electric field to polarize the material, which increases the capacitor’s ability to store charge for a given voltage. This boost in capacitance comes from the dielectric constant, εr, in the formula C = ε0 εr A / d. Air is a type of dielectric, but the standard name for the material itself is dielectric. The term insulation is too general and describes overall insulation rather than the specific capacitor material, while air gap describes the physical space, not the material name.