GREPhysics.NET: GR8677 #10

GR8677 #10

Problem

GREPhysics.NET Official Solution

Electromagnetism $\Rightarrow$ }Gauss' Law

Only choices C, D, and E make sense, since the field at $r=0$ has to be 0. Moreover, since a uniform charge distribution is applied, the field has to increases linearly within the volume of the sphere. Choice D and E are both out, leaving just C.

Direct verification via applying Gauss' Law for the inside of the sphere: $E(4\pi r^2)=Q=\rho \frac{4}{3}\pi r^3\Rightarrow E=\frac{\rho r}{3}\propto k r$ .

Outside, all five choices converge to an inverse-square decreasing field---so, no worry there!

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Comments

Andresito
2006-03-14 22:37:41

Gauss' law E*A = Q/epsilon

Yours is an approximation.

Thanks Yosun.

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