Capacitance is the ability of a component or circuit to collect and store energy in the form of electrical charge.
Capacitors are energy storage devices that come in many sizes and shapes. It consists of two plates of conductive materials (usually a thin metal) placed between an insulator made of ceramic, film, glass or other materials, or even air.
The insulator is also known as a dielectric and increases the charging capacity of the capacitor. Capacitors are sometimes referred to as capacitors in the automotive, marine, and aerospace industries.
The inner plates are wired to two outer terminals, which are sometimes thin and long and resemble thin metal antennas or legs. These terminals can be plugged into a circuit.
Both capacitors and batteries store energy. Batteries discharge energy gradually, while capacitors discharge quickly.
For example: A capacitor attached to the flash unit of a digital camera collects energy from the camera's battery and releases it in the form of a burst when the shutter is activated. Depending on the size, the capacitor may need a second or two to gather enough energy for another flash.
The capacitor collects energy (voltage) as current passes through an electrical circuit. Both plates hold equal charge, and an equal charge flows from the negative plate while the positive plate collects charge.
When the circuit is closed, the capacitor continues to hold the energy it has collected, but there is usually a small amount of leakage.
Capacitance is expressed as the ratio of the electric charge on each conductor to the potential difference (voltage) between them.
The capacitance value of the capacitor is measured in farad (F), named after the British physicist Michael Faraday (1791–1867).
Farad is a large amount of capacitance. Most residential electrical appliances have capacitors that produce capacitance for only a very small fraction of a farad (usually as little as one-thousandth of a farad, or as little as a trillionth of a microfarad, or one-trillionth of a picocardade pF).
Supercapacitors, on the other hand, can store enormous electrical charges of thousands of farads.
Capacitance may increase if:
Capacitors are often used in electrical circuits to allow alternating current (AC) to flow while blocking direct current (DC).
Some digital multimeters offer a capacitance measurement function so technicians can: