- #1

Dobuskis

## Homework Statement

-You are given a solution to Laplace's equation inside of a cylindrical region radius R.

-Show that by redefining the radial variable r as R

^{2}/r you get a solution for outside of R.

-Grounded conducting cylinder at r=R. Using a linear combination of the solutions in the previous part, construct a solution to Poisson's equation for a line charge inside the cylinder. Do the same for outside.

-What does this have to do with the method of images.

## Homework Equations

General Laplace's and Poisson's equations

ΔF = 0, ΔF = f

## The Attempt at a Solution

I spent a while trying to check the new solution by plugging it into Laplace's equation, got a bunch of chain rule terms that made something I didn't recognize, then gave up for a while. Later I realized I might be overthinking/moving in the wrong direction.

-range of R

^{2}/r with r>R is (0,R), thus the radial inputs have the same range (0,R), thus if one is a solution to Laplace's equation in its region then the same goes for the other.

-Since solutions to Laplace's equation are also solutions to Poisson's equation then and linear combination of the two previous equations is a solution. By the method of images for a conducting surface and a line charge, the solution is the object solution minus the image solution. Thus outside the cylinder is the R

^{2}/r solution minus the r solution, for inside the r solution minus the R

^{2}/r solution.

-This is the method of images for a cylindrical surface.