What happens to the capacitance when the voltage across the capacitor increases?

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Examoogle · Accepted Answer

No effect

Explanation: Capacitance is a physical property of a capacitor determined by its geometry and the dielectric material between its plates, not by the charge stored or the voltage applied. Since $C = \frac{\epsilon A}{d}$, changing the voltage $V$ across the capacitor only changes the charge $Q$ stored on the plates ($Q = CV$) but leaves the capacitance $C$ unchanged.

Working Principle: The capacitance of a parallel plate capacitor depends solely on the area of the plates ($A$), the separation distance between them ($d$), and the permittivity of the dielectric medium ($\epsilon$). Because these physical parameters remain constant regardless of the potential difference $V$ applied across the terminals, the capacitance $C$ remains constant in linear dielectric materials.

Key Formulas: $C = \frac{\epsilon A}{d}$ — formula for parallel plate capacitance; $Q = CV$ — relationship between charge, capacitance, and voltage

Key Points: Capacitance is a geometric property dependent on physical dimensions and material properties.; The ratio of charge to voltage ($\frac{Q}{V}$) is constant for a given capacitor.; Voltage and Charge vary linearly, maintaining a constant slope equal to Capacitance.

Advantages: Predictable circuit behavior in linear systems; Constant energy storage characteristics for fixed voltage levels

Disadvantages: Voltage-dependent capacitance exists in specialized components like Varicaps or Varactors (non-linear).; Dielectric breakdown can occur if voltage exceeds the rated threshold.

Applications: General purpose energy storage; Coupling and decoupling circuits

Additional Info: In certain semiconductor devices called varactors, the junction capacitance is intentionally designed to vary with the reverse bias voltage.. For standard capacitors used in DC circuits, the assumption of constant capacitance is the fundamental basis for circuit analysis.

Answer: D is correct — Capacitance is an intrinsic physical property determined by plate geometry and material, so it remains invariant to changes in voltage.

Exam Tip: Always distinguish between linear components (like standard capacitors) and non-linear components (like varactor diodes) when discussing voltage-dependent parameters.

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