AAMC FL Practice Exam

The variable 'd' in the capacitance formula \( C = \frac{A}{d} \) represents the distance between the plates of a capacitor. In this formula, 'C' is the capacitance, 'A' is the area of one of the capacitor plates, and 'd' is the separation distance between those plates.

The rationale behind this relationship is rooted in electrostatics. A larger distance between the plates results in a weaker electric field for a given charge on the plates, hence lowering the capacitance. Conversely, if the plates are closer together, the capacitance increases because the electric field strength is greater for a given amount of charge.

Understanding this relationship is fundamental in electronics and electrical engineering, as it clarifies how the physical configuration of a capacitor affects its ability to store electric charge. In this context, the other options presented do not accurately reflect the meaning of 'd' in this specific capacitance formula. The depth of the material, diameter of the plates, and density of the material do not relate to the fundamental principle represented by the equation for capacitance.