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Capacitance is the ability of an object to store electric charge. It is measured by the charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are two closely related notions of capacitance: self capacitance and mutual capacitance.
The capacitance of a capacitor is one farad when one coulomb of charge changes the potential between the plates by one volt. [1] [2] Equally, one farad can be described as the capacitance which stores a one-coulomb charge across a potential difference of one volt. [3] The relationship between capacitance, charge, and potential difference is linear.
A capacitance meter is a piece of electronic test equipment used to measure capacitance, [1] mainly of discrete capacitors. Depending on the sophistication of the meter, it may display the capacitance only, or it may also measure a number of other parameters such as leakage , equivalent series resistance (ESR), and inductance .
Capacitance is typically measured indirectly, by using it to control the frequency of an oscillator, or to vary the level of coupling (or attenuation) of an AC signal. Basically the technique works by charging the unknown capacitance with a known current, since rearranging the current–voltage relation for a capacitor ,
Unlike, say, Lebesgue measure, which measures a set's volume or physical extent, capacity is a mathematical analogue of a set's ability to hold electrical charge. More precisely, it is the capacitance of the set: the total charge a set can hold while maintaining a given potential energy.
A typical ESR Meter. This one also measures capacitance. An ESR meter is a two-terminal electronic measuring instrument designed and used primarily to measure the equivalent series resistance (ESR) of real capacitors; usually without the need to disconnect the capacitor from the circuit it is connected to.
The capacitance of certain capacitors decreases as the component ages. In ceramic capacitors, this is caused by degradation of the dielectric. The type of dielectric, ambient operating and storage temperatures are the most significant aging factors, while the operating voltage usually has a smaller effect, i.e., usual capacitor design is to ...
The rated capacitance C R or nominal capacitance C N is the value for which the capacitor has been designed. Actual capacitance depends on the measured frequency and ambient temperature. Standard measuring conditions are a low-voltage AC measuring method at a temperature of 20 °C with frequencies of