Is Solving Laplace's Equation for a Dielectric Cylinder Straightforward?

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SUMMARY

The discussion focuses on solving Laplace's equation for an infinitely long hollow dielectric cylinder with a specified electric potential on its surface. The correct approach involves using cylindrical coordinates and finding a series of solutions that satisfy the boundary conditions. Participants emphasize the importance of assuming separability and utilizing resources like Wikipedia and Wolfram MathWorld for guidance on cylindrical harmonics. The complexity of the resulting equations, particularly the non-linear second-order partial differential equation for the radius function, highlights the challenges faced in this problem.

PREREQUISITES
  • Understanding of Laplace's equation and its properties
  • Familiarity with cylindrical coordinates
  • Knowledge of boundary conditions in differential equations
  • Basic concepts of linear combinations of solutions
NEXT STEPS
  • Study the application of Laplace's equation in cylindrical coordinates
  • Learn about boundary value problems and their solutions
  • Explore resources on cylindrical harmonics from Wikipedia and Wolfram MathWorld
  • Investigate methods for solving non-linear second-order partial differential equations
USEFUL FOR

Students and professionals in physics and engineering, particularly those working with electrostatics and differential equations, will benefit from this discussion.

Sam2000009
OP warned about not using the homework template
Consider an infinitely long hollow dielectric cylinder of radius a with the electricpotential V = V0 cos φ on the surface of the cylinder where φ is an angle measured around the axis of the cylinder. Solve Laplace’s equation to find the electric potential everywhere in space.Do you just plug V into (del)^2 u where u=v?

I did that but it seems too simplistic
 
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The surface of the cylinder is a boundary condition. Typically you will want to find the series of solutions to Laplace's equation in the appropriate coordinate system to the problem at hand. (Here I would guess cylindrical coordinates). There will be an infinite series of undetermined coefficients which must be chosen to match the boundary conditions.

Since Laplace's equation is a linear equation and here it is homogeneous (away from the boundary) so any linear combination of solutions is again a solution. The trick is finding those and then finding the right linear combination to match the boundary conditions.

Some details. You should be able, with a quick search, to find Laplace's equation in various coordinate systems. You then assume separability and solve.
In cylindrical coordinates you have... well just see the Wikipedia and/or Wolfram MathWorld pages on spherical harmonics and cylindrical harmonics.
 
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I did all that and a got a messy non linear second order partial differential equation for the r function (radius) which I am pretty sure is not right
 
Sam2000009 said:
I did that but it seems too simplistic.
You mean "too simple." Simplistic means "oversimplified," and it doesn't really make sense to say something is "too simplistic" because there's no right level of oversimplification. If a situation were simplified the right amount, it wouldn't be oversimplified, would it?

Sam2000009 said:
I did all that and a got a messy non-linear second-order partial differential equation for the r function (radius) which I'm pretty sure is not right.
Telling us you tried something and got the wrong answer isn't very helpful. We need to see what you did to be able to give advice. Please post your work if you want help.
 
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