A capacitor is an electronic component, of which the primary purpose is to store an electrical charge electrostatically between two plates. Since a charged capacitor will block the passage of DC, (Direct Current.) capacitors are sometimes used as decoupling components where only the flow of AC (Alternating Current.) electricity is desired.

The many different types of capacitor are named by the type of insulation, known as the dielectric, used between their plates. This insulating material has a large bearing upon the electrical characteristics of the individual type of capacitor.

Electrolytic and tantalum capacitors are types of capacitor known as ‘polarised capacitors’. This means that they have to be connected into a circuit observing the correct polarity. Failure to do so may result in anything from the component’s eventual failure to its explosion.

A capacitor’s capacitance is measured in Farads, named after the discoverer of electrical capacitance; Michael Faraday:

Microfarad (uF, MFD) = 0.000001 of a Farad or 1 x 10 to the minus six of a Farad.

Nanofarad (nF)           = 0.000000001 of a Farad or 1 x 10 to the minus nine of a Farad.

Picofarad (pF)            = 0.000000000001 of a Farad or 1 x 10 to the minus twelve of a Farad.

- For example: 1000 pF = 1 nF = 0.001 uF.

If an individual capacitor has a voltage-rating printed on it then this is the maximum in-circuit voltage that it can operate at. Anything greater than that and the capacitor’s dielectric could rupture and become breached by an arc, causing the capacitor to explode in a worst-case scenario.