What is capacitor?

Capacitor

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.

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Some articles on capacitor:

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 swollen or ... 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 ...
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 ... 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 ... electronic devices usually include instructions to discharge large or high-voltage capacitors, for instance using a Brinkley stick ...
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 ...
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 ...