What is the primary function of a capacitor in an electrical circuit?

• A. Limits current to one direction
• B. Stores electrical energy
• C. Converts alternating current to direct current
• D. Induces magnetic fields

Answer: (B)

A capacitor’s main job in a circuit is to store electrical energy in the electric field between its two plates separated by a dielectric. When you apply a voltage, charges accumulate on the plates, and the energy is stored as field energy proportional to (1/2) times the capacitance times the voltage squared. This stored energy can be released later to smooth power, provide brief current during transients, or affect timing and filtering in circuits. In a direct-current situation, once charged, a capacitor blocks further current and behaves like an open circuit; in alternating current or changing signals, it presents a frequency-dependent impedance that allows voltage changes to pass. This is distinct from diodes, which limit current to one direction; rectifiers, which convert AC to DC; and inductors, which generate magnetic fields.