# Due spheres

## Main Question or Discussion Point

We have a metal sphere of radius R in the space and resistivity p. At a distance d>R from it we have antoher sphere of metal of radius r<<R and charge q. The 2 spheres intially are at rest.
What is the initial potential energy between them?
Now the sphere accelerate and collide anelastically. What is the amount of heat Q after this process?

P.S
This is NOT an homework, but an entrance exame at the university.
The question it's very intersting and i solved it.

For me is $$\frac{1}{4 \pi ε} \frac{q^2}{d}$$
and this is for the proprieties of metals.

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kuruman
Homework Helper
Gold Member
That looks about right and can be answered using the so called coefficients of potential. How would you answer the question about the heat generated? Hint: Assume that the small metal sphere is actually a point charge $q$ that becomes uniformly distributed over the surface of the large sphere after the collision.