ECE106 Lecture Notes - Lecture 22: Electric Field, Intelligence Quotient
6 Sep 2018
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Since the charge distribution looks the same anywhere on a conducting sphere, when we look the. E field at a or b or from any point on the surface of the sphere it should be the same. Second symmetry argument is that the electric field should be radially pointing. But that is the same direction as n , E d s = en n ds = eds. But for r < r, qenc = 0 inside the conductive sphere (i. e. there is no charge inside) e = 0. Consider this, while r2 < r1, a2 < a1 by the same amount. E 1 = e 2 but opposite. This result is as if the charge q on the surface is at a point in the center. For r > r it does not matter whether the charge has spherical distribution or a point charge! So for r > r, the sphere shell is equivalent to a point charge.
