Capacitors are used in virtually any type of circuit. They have many
applications, but their operation is really basic. As electricity is not seen,
understanding the operation of a capacitor can be a bit complicated.
Even if you already know how they work, this article can help you
better visualize the current in your head, understanding a real circuit better.
How a capacitor works
AC capacitors consist of two sheets of conductive metal, separated very close by
an insulating material, such as plastic or ceramic. The conductive sheets are
so close that their atoms can see each other but not touch each other.
The dielectric will not allow the electrons to pass from one sheet
to the other.
Charging and discharging a
capacitor
Charging the capacitor
When applying an electrical voltage with Motor-run Capacitors, it will provide electrons for one pole, and
attract them for the other.
The contributed electrons will crowd in one sheet of the capacitor,
and in the other they will disappear when being absorbed by the battery. As
there is movement of electrons, there will be an electric current.
The insulating sheet will prevent the electrons from passing from
one pole to the other, being stopped.
When the atoms of the conductive sheets do not admit any excess or
lack of electrons, they will stop moving, so the current in or out of the
condenser will stop.
As long as the applied voltage is maintained, the electrons will
continue to "push" against the insulating sheet, attracted by the
opposite pole, even if they do not move.
Capacitor discharge
If there is a conductor or resistance that allows it, the electrons
will move attracted by the positively charged atoms.
Therefore an electric current will circulate until the electrons in
one sheet are the same as in the other, standing and disappearing current.
If a voltage with the opposite polarity is applied, the whole
process will be repeated although the current will flow in the opposite
direction. The sheet that previously had positive charge (lack of electrons)
will now be negative (excess of electrons). If there is no discharge circuit
that allows electrons to pass through when the voltage is disconnected, the
capacitor will remain charged indefinitely.
Therefore, it will have its own tension, the result of the potential
difference between positive and negative atoms. At the moment that it is
connected to a circuit that allows its discharge, the electrons will move until
the charges of both poles are equalized (without voltage).
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