In 1600, the English scientistWilliam Gilbertreturned to the subject inDe Magnete, and coined theNew Latinwordelectricusfrom elektron, the Greek word for "amber", which soon gave rise to the English words "electric" and "electricity." He was followed in 1660 byOtto von Guericke, who invented what was probably the firstelectrostatic generator. Other European pioneers wereRobert Boyle, who in 1675 stated that electric attraction and repulsion can act across avacuum;Stephen Gray, who in 1729 classified materials asconductorsandinsulators; andC. F. du Fay, who proposed in 1733[1]that electricity comes in two varieties that cancel each other, and expressed this in terms of a two-fluid theory. Whenglasswas rubbed withsilk, du Fay said that the glass was charged withvitreouselectricity, and, when amber was rubbed with fur, the amber was said to be charged withresinous electricity. In 1839,Michael Faradayshowed that the apparent division betweenstatic electricity,current electricity, andbioelectricitywas incorrect, and all were a consequence of the behavior of a single kind ofelectricityappearing in oppositepolarities. It is arbitrary which polarity is called positive and which is called negative. Positive charge can be defined as the charge left on a glass rod after being rubbed with silk. One of the foremost experts on electricity in the 18th century wasBenjamin Franklin, who argued in favour 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 theglassin aLeyden jarthat 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. For a reason that was not recorded, he identified the term "positive" with vitreous electricity and "negative" with resinous electricity.William Watsonarrived at the same explanation at about the same time.

Electric chargeis thephysical propertyofmatterthat causes it to experience aforcewhen close to other electrically charged matter. There are two types of electric charges, calledpositiveandnegative. Positively charged substances are repelled from other positively charged substances, but attracted to negatively charged substances; negatively charged substances are repelled from negative and attracted to positive. An object will be negatively charged if it has an excess ofelectrons, and will otherwise be positively charged or uncharged. TheSIunit of electric charge is thecoulomb(C), although in electrical engineering it is also common to use theampere-hour(Ah), and in chemistry it is common to use theelementary charge(e) as a unit. The symbolQis often used to denote a charge. The study of how charged substances interact isclassical electrodynamics, which is accurate insofar asquantum effectscan be ignored.Theelectric chargeis a fundamentalconserved propertyof somesubatomic particles, which determines theirelectromagnetic interaction. Electrically charged matter is influenced by, and produces,electromagnetic fields. The interaction between a moving charge and an electromagnetic field is the source of theelectromagnetic force, which is one of the fourfundamental forces(See also:magnetic field).Twentieth-centuryexperimentsdemonstrated that electric charge isquantized; that is, it comes in integer multiples of individual small units called theelementary charge,e, approximately equal to1.6021019coulombs(except for particles calledquarks, which have charges that are integer multiples ofe/3). Theprotonhas a charge ofe, and theelectronhas a charge of e. Charge Interaction. Suppose that you rubbed a balloon with a sample of animal fur such as a wool sweater or even your own hair. The balloon would likely become charged and its charge would exert a strange influence upon other objects in its vicinity. If some small bits of paper were placed upon a table and the balloon were brought near and held above the paper bits, then the presence of the charged balloon might create a sufficient attraction for the paper bits to raise them off the table. This influence - known as anelectric force- occurs even when the charged balloon is held some distance away from the paper bits. The electric force is a non-contact force. Any charged object can exert this force upon other objects - both charged and uncharged objects. One goal of this unit of The Physics Classroom is to understand the nature of the electric force. In this part of Lesson 1, two simple and fundamental statements will be made and explained about the nature of the electric force.Opposites attract. And likes repel.These two fundamental principles of charge interactions will be used throughout the unit to explain the vast array of static electricity phenomena. As mentioned in theprevious section of Lesson 1, there are two types of electrically charged objects - those that contain more protons than electrons and are said to be positively charged and those that contain less protons than electrons and are said to be negatively charged. These two types of electrical charges - positive and negative - are said to be opposite types of charge. And consistent with our fundamental principle of charge interaction, a positively charged object will attract a negatively charged object. Oppositely charged objects will exert an attractive influence upon each other. In contrast to the attractive force between two objects with opposite charges, two objects that are of like charge will repel each other. That is, a positively charged object will exert a repulsive force upon a second positively charged object. This repulsive force will push the two objects apart. Similarly, a negatively charged object will exert a repulsive force upon a second negatively charged object. Objects with like charge repel each other.

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