What sets RC timing — which physical attribute of a capacitor directly affects charge/discharge time via its influence on capacitance (tau = RC)?

Introduction / Context:
Timing in first-order networks depends on the time constant tau = R * C. Since tau scales with C, any physical attribute that increases capacitance increases the time constant and slows charging/discharging (for a given R). This item asks which attribute directly influences C through the parallel-plate model.

Given Data / Assumptions:

• First-order resistor-capacitor timing, tau = RC.
• Parallel-plate intuition: C ≈ epsilon * A / d.
• All other variables held constant for comparison.

Concept / Approach:
Capacitance rises with plate area A and dielectric permittivity epsilon, and falls with greater plate separation d. Therefore, increasing plate area raises C and increases tau; decreasing area lowers C and shortens tau. Packaging, lead arrangement, or nominal voltage rating do not directly determine the capacitance value in the basic model.

Step-by-Step Solution:

Verification / Alternative check:
Manufacturing techniques (e.g., multi-layer ceramic stacks, etched foils) increase effective area to realize higher capacitance in small volumes, which directly lengthens RC time constants in timing applications.

Why Other Options Are Wrong:

• Package style / lead arrangement: may affect parasitics/ESR/ESL, but do not directly set C in the simple model.
• Voltage rating: specifies safe operating voltage; it does not by itself determine C.

Common Pitfalls:
Confusing voltage rating or package with capacitance value; overlooking that dielectric constant and geometry dominate C.

Final Answer:
Plate area.