A charged disk of total charge \"Q\" and radius \"a\" lies in the xy-plane, cent

Question

A charged disk of total charge "Q" and radius "a" lies in the xy-plane, centered at the origin. The surface-charge density distribution is nonuniform, having the surface-density, at any point inside the disk at distance "r" from the center of the form a) At what value of "r" (relative to a) is s(r) equal to its average value on the disk? (Use only Gaus laws equation! Don't use Intensities) b) Derive aformula for the charge q(r) contained within a circle of any radius r, and graph this function c) Express the electric field "Ez(z)" at any point on the +z-axis as an integral over the source0charge distribution. (Start with he result for a charged ring -- draw a diagram, and explain briefly. Be sure to define every symbol you introduce. d) Grap the function Ez(z) for -?? z??
There was an attempt to this question earlier but a) the person used intensity and we havent covered it yet. part b) is a new question, and part c there were interrogation points (?) that I wasn't sure what it was standing for. and there was never a graph. and E at the end equal Ez(z) along the z axis?

Explanation / Answer

s=Q/A A=4p^2 ?E.ndA=(1/eo)?pdV ?.E=?/eo 3. The attempt at a solution a) s=Q/A=mr^2=Q/4pa^2 m=Q/(4pa^2r^2) s(r)=mr^2=Q/(4pa^2r^2)=Q/(4pa^2) right? b) I got lost here I know the average s= Q/A=Q/(4pa^2) so I would assume r is equal 1? c) s=q/A?q=sA?dq=from 0 to r ?sA=?(Q/(4pa^2))(2pr)dr=Q/2a^2(from 0 to r ?r dr) =Q/2a^2(r^2/2)=Qr^2/4a^2 right? d) e) I'm willing to go letter by letter (a) than (b)... in details

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