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I am solving some problems from "Intro to EM" by David Griffiths ( third edition)

Problem 2.26 ( attached file 2.26.jpg) and I have also attached the solution from the solution

manual (griffiths-2.26.jpg). For both part a and b I am getting different answer.

I have chosen vertex as the origin and the axis of the cone as the positive z-axis.

The bottom of the cone is toward positive z axis. Now any differential area element on the cone would be (using cylindrical coordinates) , x*d(phi)*dz , where x is the perpendicular

distance of the area element from the z-axis. But for this geometry, x=z for any point on the

cone , so dz = dx. The distance r of this area element from the origin(vertex) would be

sqrt(2)*x. I am supposed to use the formula (formula.jpg).

Why are my solutions not working ? Or is the instructor's solution manual incorrect ?

Regards

I Newton

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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# Homework Help: Finding potential difference between two points on a cone

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