Homework Help: Energy of Configuration

1. Aug 22, 2005

heman

A sphere of radius R carries a charge density kr(where k is a constant!).What will be the energy of the Configuration??

2. Aug 22, 2005

Meir Achuz

1. Find the potential phi(r) inside the sphere.
2. Integrate rho*phi/2 over the volume of the sphere.
3. The algebra is a bit complicated. I get 35pi^2k^2R^7/72, but check me for errors.

3. Aug 22, 2005

heman

Gentleman,Why won't will be find the Potential outside the sphere..
I am very much perplexed with this Energy term..This is interaction energy
Pls help logically,i can do the maths involved.!!
Pls explain the origin of energy and i think we will integrate over whole space...but i don't have clear idea.!

4. Aug 22, 2005

heman

Well i got the solution as 4pi*k^2*R^7/21*epsilon!!
I don't know whether you are correct or me!

5. Aug 22, 2005

mukundpa

The energy is due to the work done in configuring the sphere. Consider the sphere of radius r, and add a layer of thickness dr. Calculate the work dw is required to put this layer of charge. Integrate the work dw over the radius 0 to R. This will be the energy of the configuration