Factors influencing parallel-plate capacitance For an ideal parallel-plate capacitor (with uniform dielectric), the capacitance C depends on which geometrical and material parameters, and which of the following does it NOT depend on?

Introduction / Context:
For a basic parallel-plate capacitor, the capacitance is C = ε0 εr A / d, where A is the overlapping area of the plates, d is the separation, ε0 is vacuum permittivity, and εr is the relative permittivity of the dielectric. Understanding which variables matter (and which do not) helps in practical capacitor design and scaling.

Given Data / Assumptions:

• Idealized geometry: large plates with negligible fringing effects.
• Uniform dielectric completely filling the gap.
• No dependence on frequency or losses (purely electrostatic C).

Concept / Approach:

From C = ε0 εr A / d, capacitance increases with plate area and dielectric permittivity and decreases with plate separation. The physical thickness of the metal plates does not appear in the formula, provided they are good conductors forming equipotential surfaces. Thus, thickness does not affect capacitance in the ideal model (though it affects ESR, mechanical strength, and thermal behavior).

Step-by-Step Reasoning:

Verification / Alternative check:

Electrostatic simulations and laboratory measurements show that changing plate thickness (with all other parameters fixed) does not alter C measurably until fringing or proximity effects become significant at extreme miniaturization.

Why Other Options Are Wrong:

• Area of plates, εr, and separation clearly enter the capacitance formula.
• Vacuum permittivity ε0 is part of the constant of proportionality; changing medium from vacuum to dielectric replaces ε0 by ε0 εr.

Common Pitfalls:

Assuming thicker plates “store more charge” and thus increase C; in reality, capacitance is determined by geometry of facing areas and dielectric properties, not conductor volume.

Final Answer:

Thickness of plates