A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric (insulator); for example, one common construction consists of metal foils separated by a thin layer of insulating film. Capacitors are widely used as parts of electrical circuits in many common electrical devices.

When there is a potential difference (voltage) across the conductors, a static electric field develops across the dielectric, causing positive charge to collect on one plate and negative charge on the other plate. Energy is stored in the electrostatic field. An ideal capacitor is characterized by a single constant value, capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them.

The capacitance is greatest when there is a narrow separation between large areas of conductor, hence capacitor conductors are often called plates, referring to an early means of construction. In practice, the dielectric between the plates passes a small amount of leakage current and also has an electric field strength limit, resulting in a breakdown voltage, while the conductors and leads introduce an undesired inductance and resistance.

Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass, in filter networks, for smoothing the output of power supplies, in the resonant circuits that tune radios to particular frequencies, in electric power transmission systems for stabilizing voltage and power flow, and for many other purposes.

Read more about CapacitorHistory, Non-ideal Behaviour, Capacitor Types, Capacitor Markings, Hazards and Safety

Other articles related to "capacitor, capacitors":

Lithium-ion Capacitor
... A lithium-ion capacitor (LIC) is a hybrid type of capacitor ... Activated carbon is used as cathode ...
Motor Capacitor - Dual Run Capacitors
... A dual run capacitor supports 2 electric motors, such as in large air conditioner or heat pump units, with both a fan motor and a compressor motor ... The dual capacitor has 3 terminals labeled "C", "FAN", and "HERM" for the common, fan, and hermetic compressor connections ... Round dual run capacitors (shaped as round cylinders) are commonly used for air conditioning, to help in the starting of the compressor and the condenser fan motor ...
Reservoir Capacitor
... A reservoir capacitor is a capacitor that is used to smooth the pulsating DC from an AC rectifier ... The reservoir capacitor releases its stored energy during the part of the AC cycle when the AC source does not supply any power ...
Capacitor - Hazards and Safety
... Capacitors may retain a charge long after power is removed from a circuit this charge can cause dangerous or even potentially fatal shocks or damage connected equipment ... device such as a disposable camera flash unit powered by a 1.5 volt AA battery contains a capacitor which may be charged to over 300 volts ... procedures for electronic devices usually include instructions to discharge large or high-voltage capacitors, for instance using a Brinkley stick ...
Motor Capacitor - Failure Modes
... A faulty run capacitor often becomes swollen, with the sides or ends bowed or bulged out further than usual it can be clear to see that the capacitor has failed because it is ... Some capacitors are built with a "Pressure Sensitive Interrupter" design that causes them to fail before internal pressures can cause serious injury ... One design causes the top of the capacitor to expand and break internal wiring ...