Point charges can effectively approximate charged bodies when the sizes of these bodies are significantly smaller than the distances separating them. This approximation simplifies calculations, particularly in electric field analysis, as the differences between the fields of various shapes, such as cubes and tetrahedrons, become negligible at considerable distances. The "size of the body" refers to the largest dimension across the object, which must be small relative to the observation distance for the approximation to hold true.
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Thanks for the reply. I appreciate it.Ibix said:The electric field of a charged cube, for example, is different from a charged tetrahedron. Very far from the object, though, the differences are negligible, and the difference from the field of a point charge is negligible. So we can just treat it as a point charge and save ourselves from some nasty integrals.
The size of the body, in this context, isn't really precisely defined, since we're talking about an approximation. It's something like the largest distance there is across the object. You need to be much further away than that.