Capacitance

Capacitance, pronounced kuh PAS uh tuhns, is the property of a capacitor that determines the amount of electric charge it can store. A simple capacitor consists of two metal plates parallel to and slightly apart from each other. Wires connect one plate to the positive terminal of a battery and the other plate to the negative terminal. As a result, the plates receive equal but opposite charges. These charges create an electrostatic charge, which results from the attraction that the opposite electric charges have for each other. A capacitor with large plates and a small separation distance stores a greater electrostatic charge than one with small plates and a large separation.

Capacitance is determined by dividing the charge in one of the plates, measured in coulombs, by the voltage of the battery. If 1 volt charges each plate with 1 coulomb, the capacitance equals 1 farad, the basic unit used to measure capacitance. However, 1 farad is an enormous capacitance. Most capacitors used in electronic circuits have capacitances designated in microfarads or in picofarads. A microfarad is equal to one-millionth of a farad, and a picofarad equals one-millionth of a microfarad.

Contributor: Robert B. Prigo, Ph.D., Prof. of Physics, Middlebury College.

Capacitance

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