THE PROPERTY OF CAPACITANCE
المؤلف:
S. Gibilisco
المصدر:
Physics Demystified
الجزء والصفحة:
380
14-10-2020
1737
THE PROPERTY OF CAPACITANCE
Imagine two huge flat sheets of metal that are excellent electrical conductors. Suppose that they are each the size of the state of Nebraska and are placed one over the other, separated uniformly by a few centimeters of air. If these two sheets of metal are connected to the terminals of a battery, they will become charged, one positively and the other negatively. This will take a little while because the sheets are so big.
If the plates were small, they would both become charged almost instantly, attaining a potential difference equal to the voltage of the battery. However, because the plates are gigantic, it takes awhile for the negative plate to “fill up” with electrons, and it also takes some time for the positive plate to get electrons “sucked out.”
Ultimately, the potential difference between the two plates becomes equal to the battery voltage, and an electrical field exists in the space between the plates. This electrical field is small at first; the plates don’t charge right away. However, the field increases over a period of time, depending on how large the plates are, as well as on how far apart they are. Energy is stored in this electrical field. Capacitance is a manifestation of the ability of the plates, and of the space between them, to store this energy. In formulas, capacitance is symbolized by the italicized uppercase letter C.
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