Electric charge

Electric charge (symbol q, sometimes Q) is a <a href="/facts/Physical_property/ujcMUceW">physical property</a> of <a href="/facts/Matter/osyc04UN">matter</a> that causes it to experience a <a href="/facts/Force/LNAUWMwK">force</a> when placed in an <a href="/facts/Electromagnetic_field/MacraS8y">electromagnetic field</a>. Electric charge can be positive or negative. Like charges repel each other and unlike charges attract each other. An object with no net charge is referred to as <a href="/facts/Neutral_particle/pQbmxaaE">electrically neutral</a>. Early knowledge of how charged substances interact is now called <a href="/facts/Classical_electrodynamics/vK0YI6dj">classical electrodynamics</a>, and is still accurate for problems that do not require consideration of <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum effects</a>.
In an isolated system, the total charge stays the same - the amount of positive charge minus the amount of negative charge does not change over time. Electric charge is carried by <a href="/facts/Subatomic_particle/tMEzcTWQ">subatomic particles</a>. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the <a href="/facts/Atomic_nucleus/orpIm5Xl">nuclei</a> of <a href="/facts/Atom/69syB8dH">atoms</a>. 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 <a href="/facts/Charge_quantization/lPcj6CoQ">quantized</a>: it comes in integer multiples of individual small units called the <a href="/facts/Elementary_charge/lPcj6CoQ">elementary charge</a>, e, about 1.602×10−19 C, which is the smallest charge that can exist freely. Particles called <a href="/facts/Quark/hwuuVkV5">quarks</a> have smaller charges, multiples of ⁠1/3⁠e, but they are found only combined in particles that have a charge that is an integer multiple of e. In the <a href="/facts/Standard_Model/LhVGf9ow">Standard Model</a>, charge is an absolutely conserved quantum number. The proton has a charge of +e, and the electron has a charge of −e.
Today, a negative charge is defined as the charge carried by an <a href="/facts/Electron/L0KBo5cW">electron</a> and a positive charge is that carried by a <a href="/facts/Proton/clCjepXP">proton</a>. Before these particles were discovered, a positive charge was defined by <a href="/facts/Benjamin_Franklin/Dmfv5URr">Benjamin Franklin</a> as the charge acquired by a glass rod when it is rubbed with a silk cloth.
Electric charges produce <a href="/facts/Electric_field/tt4MooBs">electric fields</a>. A moving charge also produces a <a href="/facts/Magnetic_field/Ta8Ev588">magnetic field</a>. The interaction of electric charges with an electromagnetic field (a combination of an electric and a magnetic field) is the source of the <a href="/facts/Lorentz_force/aq1Rc3SS">electromagnetic (or Lorentz) force</a>, which is one of the four <a href="/facts/Fundamental_interaction/WrFEJaFl">fundamental interactions</a> in <a href="/facts/Physics/a7aH2y08">physics</a>. The study of <a href="/facts/Photon/mFNhAEzA">photon</a>-mediated interactions among charged particles is called <a href="/facts/Quantum_electrodynamics/zPteAr6G">quantum electrodynamics</a>.
The <a href="/facts/SI_derived_unit/RLu52lWy">SI derived unit</a> of electric charge is the <a href="/facts/Coulomb/WNV9ueGr">coulomb</a> (C) named after French physicist <a href="/facts/Charles-Augustin_de_Coulomb/T4EEdFIq">Charles-Augustin de Coulomb</a>. In <a href="/facts/Electrical_engineering/YYXW1KLW">electrical engineering</a> it is also common to use the <a href="/facts/Ampere-hour/H8qKSLtk">ampere-hour</a> (A⋅h). In <a href="/facts/Physics/a7aH2y08">physics</a> and <a href="/facts/Chemistry/SrNqkGVm">chemistry</a> it is common to use the elementary charge (e) as a unit. Chemistry also uses the <a href="/facts/Faraday_constant/8AXVov0J">Faraday constant</a>, which is the charge of one <a href="/facts/Mole_(unit)/kCMFwCc0">mole</a> of elementary charges.

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Electric charge