What Is the Function of a Capacitor?

Marco d’Itri/CC-BY-2.0

Energy storage is the primary function of a capacitor. Capacitors are very common in many electronic components and come in different sizes with different capacitances.

Capacitors store electric energy when they are connected to a battery or some other charging circuit. They are commonly placed in electronic components and are used to maintain a power supply while the device is unplugged and without a battery for a short time. The energy within the capacitor prevents the loss of data, with an example being the RAM of a computer.

The capacitor contains two metallic plates that are separated by some form of insulation. The plates store the energy until it is needed.

There are different types of capacitors:

  • Axial electrolyc: small, low voltage, general purpose capacitor
  • High voltage disk ceramic: small size with high tolerance
  • High voltage electrolyc: used in power supplies
  • Metalized polypropylene: small size, good for up to 2 microfarad
  • Multi-layer: surface mount, high capacitance

The capacitance refers to the amount of storage capacity available. Capacitance is usually measured in the farad unit, which is the equivalent of one coulomb per volt. A coulomb is the unit of electrical charge. Both farad and coulomb are identified as standards by the International System of Units. For the capacitors in household electrical components, the capacitance can be measured in microfarad.