- #1

Kosta1234

- 46

- 1

- Homework Statement
- Energy stored in a charged sphere

- Relevant Equations
- $$ U = \frac {1}{2} \cdot \int \phi (r) \cdot \rho(r) dV $$

Hi.

When I am asked to figure out the Energy stored in a charged sphere and I use this equation: ## U = \frac {1}{2} \cdot \int \phi (r) \cdot \rho(r) dV ##

what is the potential ## \phi ( r) ## stands for? I tried to use the potential inside the sphere, because out side of the sphere ## \rho (r) = 0 ##, and I tried to sum those to up.

I'm not getting the same answer as in this equation:

$$ U = \frac {\varepsilon }{2} \cdot \int_{all space} E^2 dV $$so what ## \phi (r) ## I've to use and why?Edit: I got it right, I think.

was I right when I said to use the potential inside the sphere, because out side of the sphere ## \rho (r) = 0 ##

and to use the ## U = \frac {\varepsilon }{2} \cdot \int_{all space} E^2 dV ## to all space?

When I am asked to figure out the Energy stored in a charged sphere and I use this equation: ## U = \frac {1}{2} \cdot \int \phi (r) \cdot \rho(r) dV ##

what is the potential ## \phi ( r) ## stands for? I tried to use the potential inside the sphere, because out side of the sphere ## \rho (r) = 0 ##, and I tried to sum those to up.

I'm not getting the same answer as in this equation:

$$ U = \frac {\varepsilon }{2} \cdot \int_{all space} E^2 dV $$so what ## \phi (r) ## I've to use and why?Edit: I got it right, I think.

was I right when I said to use the potential inside the sphere, because out side of the sphere ## \rho (r) = 0 ##

and to use the ## U = \frac {\varepsilon }{2} \cdot \int_{all space} E^2 dV ## to all space?

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