Capacitors 101

Physically, a capacitor is an electical component consisting of two conducting surfaces separated by a non-conductor (dielectric). In electrical terms, a capacitor is an electrical component that stores electrical charge when voltage is applied. The closer the plates, the stronger the electric field produced. The greater the charge stored on the plates, the stonger the field produced.

This field represents the storage of electric energy. This energy comes from a source and can be returned to a circuit when the source is removed.

Once a capacitor is hooked up to a power supply, the electrons do not travel through the non-conductive dielectric material between the capacitor’s plates. This electrons accumulate on that side of the capacitor creating an excess of electrons resulting in a negative charge. The electrons orbit passes in the through the dielectric and are repelled by the negative polarity of the capacitor.

As these electrons build up creating a negative side to the capacitor, the electrons are more and more attracted to the capacitor’s positive side. Once sufficient charging current has passed to cause the capacitor’s voltage to equal the source voltage, no more current can flow. The capacitor is now fully charged.

Voltage doesn’t pass through this dielectric material but it acts that way due to the movement of electrons on either side. Once a capacitor is charged, it will equal the source voltage. If the source voltage increases/decreases, the capacitor will do so likewise.

The unit of capacitance is the farad. Common capacitors for car stereo installations would be around 1 farad. A farad is the amount of capacitance where a charge of 1 coulomb develops a potential difference of 1 volt across the capacitor plates.

C=Q/V Q=CV V=Q/C

V=Voltage

Q=Coulombs

C=Capacitance in Farads

Coulomb’s Law F=(kQ1XQ2)/(d2)

Before your charge your capacitor, you must discharge the capacitor. To do this, just short out the positive and ground leads very carefully and hold it for a few seconds to be sure that all the stored voltage is released. To properly charge a capacitor, use a resistor between your battery and your capacitor. Use roughly a 1kΩ resistor here. Hook up the resistor to the power wire and let the capacitor charge for roughly 5-25 sec.