Electric Charge

The electric charge is a fundamental property of the Matière which enables him to interact by the means of electromagnetic fields. The Force resulting from this interaction produces charged matter a movement, the Electric current.

Presentation

The electric charge is a concept abstracted, comparable with that from Masse, which makes it possible to explain certain behaviors. Contrary to the mass, the electric charge can take two forms, that the experiment brings to regard as “opposite”; they arbitrarily are qualified positive and negative . Two loads of comparable nature, two positive loads for example, are pushed back, whereas two loads of opposite nature attract each other. One calls this phenomenon electromagnetic interaction. The interaction between the loads and a electromagnetic field is the source of one of the four fundamental forces. These electromagnetic fields, in Mechanical traditional, obey the Maxwell's equations.

The electric charge can be directly measured with a electrometer. Its unit is the Coulomb. The particles observed have loads which are multiple entireties of the Elementary charge which is a Constante fundamental physics. The Quark S are supposed to have loads which are multiples of the third of the fundamental load, but these particles are not observable. The discrete nature of the electric charge was shown by Robert Millikan in the Expérience of Millikan (experiment on the oil drops).

History

The electric charge is discovered by the former Greeks who note that the friction of the fur on various substances, such as the Ambre, produces an electric imbalance of charge (phenomenon Triboélectrique). The Greeks note that amber buttons charged could attract light objects such as hair. They also notice that if they rub amber long enough, they can even obtain a spark. The word electricity drift of ηλεκτρον , the Greek word for amber .

At the 18th century, the study of electricity becomes popular. One carries out experiments of electrostatics during which, using devices playing the condensing part of S such as the Leyden jar, one reaches sufficiently high tensions to cause commotions . By a series of experiments (1733), the intendant of Fay distinguishes two kinds of electricity: vitreous electricity and resinous electricity corresponding to the two types of behavior of the matter at the time of an electrification by friction.

At the same time, Benjamin Franklin imagines electricity as being a type of invisible fluid present in all the matter. It poses as principle which the friction of insulating surfaces puts this fluid moving and which a flow of this fluid constitutes a Electric current. It also poses as principle that the matter not enough containing this fluid is negatively charged , positively charged if not. Arbitrarily, in any case for a reason which is unknown for us, it identifies the positive term with the type of load acquired by a stem of Verre rubbed on Soie, and negative with that acquired by an amber stem rubbed with Fourrure.

Convention and realities

We know now that the model of Franklin was too simple. The matter is really composed of two kinds of electricity: the particle S called Proton S which carry a positive electric charge and particles called electron S which carries a negative electric charge .

The Electric current can have various causes: a flow of negative particles or a flow of positive particles, or a flow of negative particles and positive in directions opposées.

To reduce this complexity, the electrician S always employ the convention of Franklin and, imagine the electric current, known under the name of conventional current , as made up of a flow of particles exclusively positives.

The conventional current simplifies the concepts and calculations, but mask the fact that in some conducting (electrolyte S, Semi-conducteur S, and plasma) the two types of electric charges move in opposed directions, or that in metals, the negative charges are quasi exclusively responsible for the flow of the current. These last parameters are the business of the Scientifique S of research on the subjects and of the Engineer S of design in electrotechnical and electronic.

Properties

Except the properties described in articles concerning electromagnetism, it should be noted that the load is an invariant of the Theory of relativity. This wants to say that any particle of load Q , whatever its Speed, will always keep its load Q.

See too

Tribology - localized Contacts

Conservation of the electric charge

Simple: Electric charges Zh-yue: 電荷

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