Capacitor

A passive two-terminal device that stores Energy in an Electric Field, characterized by its Capacitance.

analogy: A capacitor acts as an elastic membrane in a pipe. As water pressure changes, the membrane stretches and relaxes to transfer energy between the sides.

Capacitance (C)

Is the ability to store Energy in a Electric Field.

analogy: How easily the elastic membrane stretches. More elastic membrane means more capacitance.

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Units

Properties

  • Opposes a change in Voltage
  • Reactance leads to OC at low frequencies and SC at high frequencies
  • Voltage across a capacitor is
  • Current through a capacitor is
  • Energy stored in the electric field is
  • Total capacitance in series is
  • Total capacitance in parallel is

Physical Definition

  • Formed by a pair of closely-spaced metal plates, separated by an insulator

  • = Dielectric Constant

  • = plate area

  • = distance between plates

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