Difference between revisions of "Charge"
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| − | '''Charge''' is the [[fundamental]] property of any [[matter]] that exhibit electrostatic [[attraction]] or repulsion over other matter. Electric charge is a characteristic property of many [ | + | '''Charge''' is the [[fundamental]] property of any [[matter]] that exhibit electrostatic [[attraction]] or repulsion over other matter. Electric charge is a characteristic property of many [https://en.wikipedia.org/wiki/Charged_particle subatomic particles]. The charges of free-standing [[particles]] are integer multiples of the elementary charge e; we say that electric charge is ''quantized''. [https://en.wikipedia.org/wiki/Michael_Faraday Michael Faraday], in his [https://en.wikipedia.org/wiki/Electrolysis electrolysis] [[experiments]], was the first to note the discrete [[nature]] of electric charge. [https://en.wikipedia.org/wiki/Robert_Millikan Robert Millikan]'s oil-drop [[experiment]] [[demonstrated]] this [[fact]] directly, and measured the elementary charge. |
| − | By [[convention]], the charge of an [[electron]] is −1, while that of a [ | + | By [[convention]], the charge of an [[electron]] is −1, while that of a [https://en.wikipedia.org/wiki/Proton proton] is +1. Charged particles whose charges have the same sign repel one another, and [[particles]] whose charges have [[different]] signs [[attract]]. [https://en.wikipedia.org/wiki/Coulomb%27s_law Coulomb's law] quantifies the electrostatic [[force]] between two [[particles]] by asserting that the [[force]] is [[proportional]] to the product of their charges, and [https://en.wikipedia.org/wiki/Inverse_square inversely proportional to the square] of the distance between them. |
| − | The charge of an [ | + | The charge of an [https://en.wikipedia.org/wiki/Antiparticle antiparticle] [[equals]] that of the corresponding [[particle]], but with opposite sign. [https://en.wikipedia.org/wiki/Quark Quarks] have [[fraction]]al charges of either −1⁄3 or +2⁄3, but free-standing quarks have never been observed (the [[theoretical]] reason for this [[fact]] is [https://en.wikipedia.org/wiki/Asymptotic_freedom asymptotic freedom)]. |
| − | The electric charge of a [ | + | The electric charge of a [https://en.wikipedia.org/wiki/Macroscopic macroscopic] object is the sum of the electric charges of the particles that make it up. This charge is often zero, because [[matter]] is made of [[atoms]], and atoms all have [[equal]] numbers of [https://en.wikipedia.org/wiki/Proton protons] and [[electrons]]. More generally, in every [[molecule]], the [[number]] of [https://en.wikipedia.org/wiki/Anion anions] (negatively charged atoms) equals the number of [https://en.wikipedia.org/wiki/Cation cations] (positively charged atoms). When the net electric charge is non-zero and motionless, the [[phenomenon]] is known as [https://en.wikipedia.org/wiki/Static_electricity static electricity]. Even when the net charge is zero, it can be distributed non-uniformly (e.g., due to an external [https://en.wikipedia.org/wiki/Electric_field electric field] or to molecular [[motion]]), in which case the [[material]] is said to be [[polarized]]. The charge due to [[polarization]] is known as [https://en.wikipedia.org/wiki/Bound_charge bound charge], while the excess charge brought from outside is called free charge. The motion of charged particles (especially the motion of electrons in metals) in a given direction is known as [https://en.wikipedia.org/wiki/Electric_current electric current].[https://en.wikipedia.org/wiki/Electric_charge] |
[[Category: Physics]] | [[Category: Physics]] | ||
Latest revision as of 23:45, 12 December 2020
Charge is the fundamental property of any matter that exhibit electrostatic attraction or repulsion over other matter. Electric charge is a characteristic property of many subatomic particles. The charges of free-standing particles are integer multiples of the elementary charge e; we say that electric charge is quantized. Michael Faraday, in his electrolysis experiments, was the first to note the discrete nature of electric charge. Robert Millikan's oil-drop experiment demonstrated this fact directly, and measured the elementary charge.
By convention, the charge of an electron is −1, while that of a proton is +1. Charged particles whose charges have the same sign repel one another, and particles whose charges have different signs attract. Coulomb's law quantifies the electrostatic force between two particles by asserting that the force is proportional to the product of their charges, and inversely proportional to the square of the distance between them.
The charge of an antiparticle equals that of the corresponding particle, but with opposite sign. Quarks have fractional charges of either −1⁄3 or +2⁄3, but free-standing quarks have never been observed (the theoretical reason for this fact is asymptotic freedom).
The electric charge of a macroscopic object is the sum of the electric charges of the particles that make it up. This charge is often zero, because matter is made of atoms, and atoms all have equal numbers of protons and electrons. More generally, in every molecule, the number of anions (negatively charged atoms) equals the number of cations (positively charged atoms). When the net electric charge is non-zero and motionless, the phenomenon is known as static electricity. Even when the net charge is zero, it can be distributed non-uniformly (e.g., due to an external electric field or to molecular motion), in which case the material is said to be polarized. The charge due to polarization is known as bound charge, while the excess charge brought from outside is called free charge. The motion of charged particles (especially the motion of electrons in metals) in a given direction is known as electric current.[1]
