Electric charge: Difference between revisions

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'''Electric charge''' is the [[physical property]] of [[matter]] that causes it to experience a [[force]] when placed in an [[electromagnetic field]]. There are two types of electric charge: ''positive'' and ''negative'' (commonly carried by [[proton]]s and [[electron]]s respectively). Like charges repel each other and unlike charges attract each other. An object with an absence of net charge is referred to as '[[neutral particle |neutral]]. Early knowledge of how charged substances interact is now called [[classical electrodynamics]], and is still accurate for problems that do not require consideration of [[quantum mechanics|quantum effects]].
Electric charge is a [[conservation law (physics)|conserved property]]; the net charge of an [[isolated system]], the amount of positive charge minus the amount of negative charge, cannot change. Electric charge is carried by [[subatomic particle]]s. In ordinary matter, negative charge is carried by [[electron]]s, and positive charge is carried by the [[proton]]s in the [[atomic nucleus|nuclei]] of [[atom]]s. If there are more electrons than protons in a piece of matter, it will have a negative charge, if there are fewer it will have a positive charge, and if there are equal numbers it will be neutral. Charge is ''[[charge quantization|quantized]]''; it comes in integer multiples of individual small units called the [[elementary charge]], ''e'', about {{val|1.602|e=-19|u=coulombs}},{{physconst|e|ref=only}} which is the smallest charge which can exist freely (particles called [[quark]]s have smaller charges, multiples of {{sfrac|1|3}}''e'', but they are only found in combination, and always combine to form particles with integer charge). The [[proton]] has a charge of +''e'', and the [[electron]] has a charge of −''e''.