Introduction to electromagnetism: Difference between revisions

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== Electric charge ==

[[Electric charge]] is a quantity used to determine how a particle will behave in an [[electric field]]. There are three possible "types" of charge: positive, negative, and neutral. Neutral particles do not accelerate in an electric field, whilst positive and negative charges accelerate in opposite directions. However, thewhich distinctioncharge betweenis the positive and which is the negative is bya matter of naming convention only.<ref name=":0">{{Cite book|title=Electricity and Magnetism, Third Edition|last=Purcell|first=Edward M.|publisher=Cambridge University Press|year=2013|isbn=978-1107014022|___location=Cambridge|pages=2–4}}</ref> Electric charge is quantized in units of the [[elementary charge]], <math>e</math>, where a proton has a charge of <math>+e</math> and an electron has a charge of <math>-e</math>. The [[International System of Units|SI unit]] of charge is the [[coulomb]].<ref name=":1">{{SIbrochure8th}}.</ref> [[File:Simplified scheme of Millikan’s oil-drop experiment.svg|thumb|Millikan's oil drop experiment.]]

The elementary charge <math>e</math> was first measured by [[Robert Andrews Millikan|Robert Millikan]] in his [[oil drop experiment]] in which the electric force on the particle is set to exactly counter the [[Gravity|gravitational force]] that pulls it down, and the [[terminal velocity]] of this particle can be used to calculate its charge.<ref>, Millikan discussing his work and subsequent improvements.</ref> A neutron has no electric charge.