Capacitor is a device used to__________

Question

Examoogle · Accepted Answer

store electrical energy

Explanation: A capacitor is a passive two-terminal electronic component that stores electrical energy in an electric field. When a potential difference is applied across its plates, charge accumulates, creating an electrostatic field between the dielectric medium.

Working Principle: When connected to a DC voltage source, electrons move from one plate to another through the external circuit until the potential difference across the plates equals the source voltage. This movement creates a displacement current and stores charge $Q = CV$. The energy is held in the electric field created by the separation of positive and negative charges on the capacitor plates.

Key Formulas: $E = \frac{1}{2}CV^2$ — Energy stored in the electric field; $Q = CV$ — Relationship between charge, capacitance, and voltage; $C = \frac{\epsilon A}{d}$ — Capacitance in terms of geometry

Key Points: Capacitors act as open circuits to DC steady-state current.; The energy storage is reversible; discharging returns the energy to the circuit.; The dielectric material between plates determines the permittivity ($\epsilon$).; Capacitors are essential in filtering, decoupling, and timing circuits.

Advantages: Rapid charge and discharge cycles.; High reliability and long operational life compared to batteries.

Disadvantages: Limited energy density compared to chemical batteries.; Subject to leakage current and dielectric breakdown.

Applications: Power supply filtering; Signal coupling and decoupling; Energy storage for pulsed power; Tuning in radio frequency circuits

Additional Info: Option B (vary resistance) refers to a Rheostat or Potentiometer.. Option C (store magnetic energy) describes an Inductor, which stores energy in a magnetic field ($E = 1/2 LI^2$).. Option D (dissipate energy) describes a Resistor, which converts electrical energy into heat.

Answer: A is correct — A capacitor is a fundamental passive component designed specifically to store electrical energy within an electric field.

Exam Tip: Always distinguish between Capacitors (store electrical energy in E-fields) and Inductors (store magnetic energy in H-fields); they are the inverse of each other in many AC circuit equations.

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