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## Homework Statement

Consider a uniformly charged solid cylinder of radius R, length L and charge density ρ. Find the

potential at a distance d (> L/2) from the centre of the object, along the axis of the cylinder.

## Homework Equations

V=∫kdq/r

## The Attempt at a Solution

For me, it makes most sense to express this integral in cylindrical coordinates, seeing as the object is a cylinder. Also, since the axis of which the cylinder is on is not specified. I chose the z axis on a (x,y,z).

-stuff used for integration, respectively.

s[0,R]

Ø[0,2π]

z[0,L]

dq=sdsdØdz

I'm not too good at expressing notation on the computer so this is the basics of what i tried:

1st attempt: I know V(z)=∫E.dl , so, I tried to solve for E by using

E=∫kdq/r^2

E=∫∫∫(kρ/z^2)sdsdØdz

after I finished this integral, I lost confidence when doing the integral for V(z) because It didn't seem right to integrate over the same limits of integrations seeing as dl would be expressed as sdsdØdz - please tell me if i'm wrong.

2nd attempt: I just started with V=∫kdq/r.

V=∫∫∫(kρ/z)sdsdØdz

giving me

V(z)=kρπ*ln(z)*R^2

- I'm not sure which method is correct, if either. Help would be greatly appreciated.

- Also, since were just looking for the function with respect to a distance and because of the way the question was stated, I felt that it was okay to express r as just z rather than (L/2 + z)