A capacitor is made of two identical metal plates separated by air. What parameters determine its capacitance?

The capacitance of a parallel-plate capacitor is determined by its physical construction, specifically the surface area of its plates, the spacing (distance) between them, and the type of dielectric material separating them. Since this question specifies an air dielectric, the determining parameters are just the surface area and the plate spacing. A larger surface area provides more physical space to store an electric charge, thereby increasing capacitance. Conversely, moving the plates further apart weakens the electric field between them, which decreases the total capacitance. Distractors that mention applied voltage, operating frequency, or the type of metal are incorrect. The type of metal conducts the charge but does not affect the storage capacity. While voltage and frequency affect how the capacitor reacts within a live circuit, they do not alter its structural capacitance value.