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Q is a measurement of the charge held by an object. The SI unit of electric charge is the coulomb, which represents approximately 6.24 x 1018 elementary charges (the charge on a single electron or proton). The coulomb is defined as the quantity of charge that has passed through the cross-section of a conductor carrying one ampere within one second. (see Ampere)
Electric charge can be directly measured with an electrometer. The discrete nature of electric charge was demonstrated by Robert MillikanRobert Andrews Millikan ( March 22, 1868 December 19, 1953) was an American physicist who won the 1923 Nobel Prize for Physics primarily for his work in determining the value of the charge on the electron and for the photoelectric effect. He later worked in his oil-drop experimentThe purpose of Robert Millikan's oil-drop experiment ( 1909) was to measure the electric charge of the electron. He did this by carefully balancing the gravitational and electric forces on tiny charged droplets of oil suspended between two metal electrode.
Formally, a measure of charge should be a multiple of the elementary charge e, but since it is an average, macroscopicMacroscopic means measurable and observable by the naked eye; describes existence as we perceive it. For instance, a macroscopic view of a ball is just that: a ball. A microscopic view could reveal a thick round skin seemingly composed entirely of puckere quantity, many orders of magnitude larger than a single elementary charge, it can effectively take on any real valueIn mathematics, the real numbers are intuitively defined as numbers that are in one-to-one correspondence with the points on an infinite line—the number line. The term "real number" is a retronym coined in response to " imaginary number". Real numbers may.
Charge was discovered by the Ancient GreeksAncient Greece is the term used to describe the Greek-speaking world in ancient times. It refers not only to the territory of the present Greek state, but also to those areas settled in ancient times by Greeks: Cyprus, the Aegean coast of Turkey (then kno who found that rubbing furFor alternative meanings, see Fur (disambiguation). The term fur refers to the body hair of non-human mammals also known as the pelage (like the term plumage in birds). True fur comes from animals where the coat consists of short ground hair, long guard h on various substances, such as amber, would build up an electric charge imbalance. The Greeks noted that the charged amber buttons could attract light objects such as hair. The Greeks also noted that if they rubbed the amber for long enough, they could even get a spark to jump. This property derives from the triboelectric effect. The word electricity derives from ηλεκτρον, the Greek word for amber.
It was noticed that electricity seemed to come in two varieties, that cancel each other, and this was expressed in terms of a two-fluid theory. When glass is rubbed with silk, the glass was said to be charged with vitreous electricity, and when amber was rubbed with fur, the amber was said to be charged with resinous electricity.
By the 18th century, the study of electricity had become popular. One of the foremost experts was Benjamin Franklin, who argued in favor of a one-fluid theory of electricity. Franklin imagined electricity as being a type of invisible fluid present in all matter, for example he believed that it was the glass in a Leyden jar that held the accumulated charge. He posited that rubbing insulating surfaces together caused this fluid to change location, and that a flow of this fluid constitutes an electric current. He also posited that when matter contained too little of the fluid it was "negatively" charged, and when it had an excess it was "positively" charged. Arbitrarily (or for a reason that was not recorded) he identified the term "positive" with vitreous electricity and "negative" with resinous electricity.
We now know that Franklin's model was close, but too simple. Matter is actually composed of several kinds of electrically charged particles, most common are the positively charged proton and the negatively charged electron. Rather than one possible electric current there are many: a flow of electrons, a flow of electron "holes" which act like positive particles, or in electrolytic solutions, a flow of both negative and positive particles called ions moving in opposite directions. To reduce this complexity, electrical workers still use Franklin's convention and they imagine that electric current (known as conventional current) is a flow of exclusively positive particles. The conventional current simplifes electrical concepts and calculations, but it ignores the fact that within some conductors (electrolytes, semiconductors, and plasma,) two or more species of electric charges flow in opposite directions. The flow direction for conventional current is also backwards compared to the actual electron drift taking place during electric currents in metals, the typical conductor of electricity, which is a source of confusion for beginners in electronics.
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