A capacitor or condenser is a passive two-terminal electrical component used to store energy electrostatically in an electric circuit. Capacitors vary widely, but all contain at least two electrical conductors (plates) separated by an insulator.

When a potential difference across the conductors (when a capacitor is attached across a battery), an electric field develops across the dielectric, causing a positive charge to collect on one plate and a negative charge to collect on the other plate. If a battery has been attached to a capacitor for enough time, no current can flow through the capacitor. But, if an accelerating or alternating voltage (AC) is applied across the leads of the capacitor, a displacement current can flow.

An ideal capacitor is characterised by a single constant value for its capacitance. Capacitance is expressed as the ratio of the electric charge on each conductor to the potential difference (V = Voltage) between them. The SI (International System of Units SI is abbreviated from the French Système international (d'unités), the modern form of the metric system) unit of capacitance is the farad (F) which is equal to one coulomb per volt (1 C/V). Typical capacitance values range from about 1 pF (10−12 F) to about 1 μF (10−3 F).

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The capacitance of a Capacitor

Capacitance is the electrical aspect of a capacitor and measures a capacitor's ability to store an electrical charge onto its twin plates. The unit of capacitance is a Farad (F).

Capacitance is defined as being that a capacitor has the capacitance of One Farad when a charge of One Coulomb is stored on the plates by a voltage of one volt. Capacitance (C) is constantly positive (+ve) in value, having no negative units (-ve). However, the Farad is an exceptionally large unit of measurement to use on its own, so sub-multiples of the Farad are generally used, such as micro-farads, nano-farads, or pico-farads.

Standard Units of Capacitance

  • Microfarad (μF) 1μF = 1/1,000,000 = 0.000001 = 10-6 F

  • Nanofarad (nF) 1nF = 1/1,000,000,000 = 0.000000001 = 10-9 F

  • Picofarad (pF) 1pF = 1/1,000,000,000,000 = 0.000000000001 = 10-12 F

Using the information above a simple table can be applied to help convert pico-Farad (pF), nano-Farad (nF), micro-Farad (μF), and Farads (F) as indicated below.

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Capacitors are a crucial component in Model kit builds with dynamic lighting and sound modifications.