Electrical capacitance capacitor - a physical quantity which characterizes the process of charging conductors separated by a dielectric layer. Uses numerous mathematical calculations, is marked on the product.
Electrical capacitance of the capacitor is usually expressed through stocking up on a charge q at an applied voltage U in this way:
C = q / U.
The origin of the formula - enigma. The only known: From Gauss' theorem on the electric field intensity find electrical capacitance of the capacitor. Who spent calculating, never said. Physical quantity farad originally GHS system was absent, in 1861 introduced a special commission formed by physicists.
According to anecdotal evidence, the first electrical capacitance of the capacitor determined who coined the terms in everyday life. Mean Alessandro Volta. Late 70th (XVIII century), the scientist has given research question set: electrical capacitance can be expressed in terms of the stored charge, the voltage applied to the electrodes.
In addition, often manage to find a formula of a plane capacitor electric capacity:
The author avoids judge who dealt calculation expression. Logically speaking, very few people are interested in electric capacity flat capacitor before the birth Polak invention. Leyden jar differently distribute the charge. Reasoning leads to the beginning of the XX century. Perhaps the issue is dealt with Tesla, Hertz. With less likely - Popov.
Families are named on the criteria of interest ac. Tesla studied electrical safety issues, over a distance, designed engines. Hertz and Popov investigated antenna deliberately tuned to a certain wavelength, which is easier to obtain by applying an oscillating circuit. Consequently, researchers are required to have an idea of the electric capacity of the capacitor, inductors.
James Maxwell, Lord Kelvin, William Weber paid much attention to the improvement of a unified system for measuring physical quantities. Probably someone had a hand in the study of capacitors. One thing is clear - in the history of the world of natural sciences mass of blind spots when it comes to Russian-language sources. Portal VashTehnik one of the first to begin to publish the latest research in the field of the correct understanding of the events.
Impatient readers reported: Alessandro Volta introduced proper term capacity. It is not known exactly, used anyone before, but in his work the Italian scientist, calling elektroforus capacitor simultaneously applies the term capacity. As the vessel where you can "pour" the charge of the vessel. Condenser calls for the similarity with the vapor deposition process: slowly we type an arbitrary amount of electricity. By and large, this is true.
The term capacitor
Historically, the first capacitor is considered a Leyden jar. Disputes still go, who invented the device, because the two scientists, enthusiastic events avoided doing accurate records. One thing is certain - the device electric capacity could not be measured, there was no corresponding term "electrical capacitance of the capacitor."
Screen printed version of the treatise Volta, 1782
Coined the term powerless Pronounce earlier than Alessandro Volta in 1782, reporting Royal Society research in the field of electrostatics to understand the origin of the electricity. It is known, for the next five years, Luigi Galvani open "animal electricity", Volta led directly to the creation of the first battery. Reporting to the public, the young scientist deprived of said knowledge, shining trying to figure out where the charge appears. Says something like this: "There are currently a lot of evidence of the existence of atmospheric electricity. People are powerless to find traces of presence. Probably means: by electroscopes too weak, unable to grasp such a delicate matter. Consequently, the need to find a way to take away from the air vibes. "
Performing said, Alessandro Volta offers a device called elektroforusom (not to be confused with an electrostatic machine). Device captures fluids conductor atmospheric (air). The principle of serving Volta resembles condensation process: collecting electricity.
elektroforus West calls capacitive generator. The above makes it possible to believe: this definition clung thanks written by British Royal Society Volta. The device invented by another man - a Swedish physicist John Clark Fork. It happened two decades earlier - in 1762.
Now it considered the popularity of the instrument gave Volta, calling eternal pet electricity generator. Also essentially correct, rub the rubber can be thousands of years. More "capacitor" recalls (see. Fig.) hefty printing. From above, in addition to the main central pens, stands side - removal of negative potential. We see three layers:
- The substrate is optional, it is glued tires.
- Thin rubber layer serves as an electrifying body by friction.
- Top - thin sheet metal, provided with two handles, one (central) isolated.
Getting started, you need to remove the "print", rub the rubber coat. Then smooth disk is put back. The area of contact with the rubber is low due to the presence of roughness, a positive charge is acquired soon. It is necessary to wait. Operator for a brief moment grounds cover the side handle, remove the negative charge, the bottom remains positive. With one hand touching the metal can be heard well audible crackling. Rubber after lifting the lid has an excess of electrons, allowing to repeat the experience several times (hard to believe, some sources speak of hundreds of repetitions).
Unscrambling the body, abruptly pulling insulating handle, the operator is static electricity. The invention is a revolutionary, remarkable, appeared in a few years after the repeal of the witch hunt. According to the statement of Volta, a circle of rubber made as thin as possible within a 50th of an inch. Can not get the best result. Sheet metal plate effectively becomes. Otherwise we will have to wait a long time filling volume conductor. The common people, "capacitor" refers to rubber cake. Pie coated with a metal filling.
Are elektroforus is an inexhaustible source of energy? Under ideal conditions, although hard to believe. Negative charge rubber polarizes the metal plate, creating a potential. Extruded on the outer surface of electrons removed earthing touch. It remains to separate the components of elektroforusa. Destroying the positive charge of touch, hearing the sound of Skip spark, you can re-start experience.
Elektroforus really looks like a capacitor. After removing the excess of negative charge becomes actually in said device. Long capacitor can not be stored because electrons with rubber will gradually flow down to the metal. The device is discharged. In fact, rubber, metal separated from one another by air serving as a dielectric. Instead of using different rubber polymers, such as Teflon.
It remains to note: in the time of Volta did not know the methods of getting rid of the rubber static charge. "Facing" capacitor can be stored for a long time load of electrons. Volta offers for discharging the sample is placed under the rays of the sun, or could move next to a burning candle. After flame ionized electrons leave the condenser. Today, it is clear, wash the rubber enough to trace remained static. To work need to re-dry.
It is believed that Felix Savary discovered resonance circuit oscillations. Discharging a Leyden jar through the twisted strand of copper observed erratic warping of the compass. In 1826, when Britain, France, Germany, Italy partially feverishly researched new phenomenon, the introduction into the scientific world Oersted.
The history of the Leyden jar can be found in the respective review. It must be said, no one has really tried to understand what the electrical capacitance of the capacitor. It is not necessary for obvious reasons: Leyden jar mainly used academia, solving specific problems. Experience Felix Savary long go unnoticed ...
In 1842, the oscillating circuit, electric capacity of the condenser took up our old friend, Sir Joseph Henry, the inventor of the electromagnetic relay, a lover of the telegraph. I set out in writing after testing notes Savary practice:
"The anomaly, which remains so long without an explanation, which at first glance seems counter to the existing our theory of electricity and magnetism, after careful study I referred to the hitherto unknown phenomena. Discharge is strange (contrary to Franklin's theory), feeling that, coming out of the banks, the fluid starts to wander back and forth. Seen forces admit the process begins in the normal way, then there is some change of direction each time the amplitude becomes smaller as the movement fades out altogether. Apparently, the phenomenon of today can not be explained by physics met with him (Savary), but were powerless. "
Obviously, scientists are not interested in electrical capacitance of the capacitor - thoughts absorbed anomalies that would like to explore. Five years later, read the report Henry physicist Helmholtz at the meeting of the Physical Society of Berlin, he says:
"Through electrolysis notice unusual fluctuations. A feeling vibrations process continues until the self vis viva disappears permanently absorbed total circuit resistance. The impression is on a path of current flowing two opposite directions, the top takes one or the other. "
Put an end to disputes famous William Thomson, Lord Kelvin betrothed. Mathematically investigate the processes stated in the chain there are obviously two things: the electrical capacitance of the capacitor and the inductance of the coiled copper wire. Work On Transient Electric Currents become a classic. Although Lord Thomson calling electrodynamic inductance capacitance, meaning the formula unambiguous. The first scientist said energy is transferred between the capacitor and the inductor, gradually fading to active resistance circuit.
The formula shown in the figure given in modern values, a standard notation. C - electrical capacitance of the capacitor, L - inductance of the coil, q - charge quantity, I - circuit current. Other symbols refer to the operation of differentiation. The term inductance introduced much later - in 1886 by Oliver Heaviside. The formula of the resonance frequency, which depends on the electrical capacity of the capacitor and inductors, derived James Clerk Maxwell in 1868 year.