线电荷和点电荷之间有什么区别?


回答 1:

线电荷在一个方向上具有物理尺寸,该物理尺寸沿该方向分配电荷。

Theonlythingthatphysicallyexistsisavolumecharge.Everythingelseisanapproximationtosimplifythemath.ApointchargeisinfinitelysmallinalldirectionssoitcanonlybedescribedbyatotalchargeQ.Allfinitevolumechargeslooklikepointchargesifyouarefarenoughawayfromthem.The only thing that physically exists is a volume charge. Everything else is an approximation to simplify the math. A point charge is infinitely small in all directions so it can only be described by a total charge Q. All finite volume charges look like point charges if you are far enough away from them.

Thinkofalinechargeasapointchargestretchedinonedirection.Linechargeshavezerosizeintwodirectionandsomelengthinthethirddirection.IfthatlengthisL,thenwecandescribethelinechargebybothitstotalcharge[math]Q[/math]anditslinechargedensity[math]ρell=Q/L[/math].Think of a line charge as a point charge stretched in one direction. Line charges have zero size in two direction and some length in the third direction. If that length is L, then we can describe the line charge by both its total charge [math]Q[/math] and its line charge density [math]\rho_{\rm{ell}} = Q/L[/math].

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