# Coulomb's Law in free space

What information does this law give us?

This seems to be a different question to "what does this law mean?", which I could answer with "it describes the electrostatic force between two charges q1 and q2 seperated by a distance r, the magnitude is inversely proportional to the square of the distance between them, and the force is either repulsive or attractive.. etc"

Does that answer the question, or is there some information that can be gotten from Coulomb's Law?

I'm pretty confused with this one!

Thanks

## Answers and Replies

Sigma Rho said:
What information does this law give us?

This seems to be a different question to "what does this law mean?", which I could answer with "it describes the electrostatic force...
You just answered your own question. Whenever you describe something, you provide information.

turin
Homework Helper
You can sort of wave your hands and say that, since it is an inverse square law, the interaction is mediated by isotropic emission of some particle. How? Because, as you get further away, the likelyhood of one of these particles colliding with a charge drops off as the square of the distance (which is justifiable with geometry, i.e., pre-physical).

robphy
Science Advisor
Homework Helper
Gold Member
Sigma Rho said:
"it describes the electrostatic force between two charges q1 and q2 seperated by a distance r, the magnitude is inversely proportional to the square of the distance between them, and the force is either repulsive or attractive.. etc"

A comment on semantics:
In this context, the word "between" can be troublesome to some students, for example, when asked to draw the force.
A better phrase is the "electrostatic force on one charge due to the other".

What information does this law give us?

I could be off base here, but I see Coulomb's law as nothing more than a concequence of Gauss's law, so you should really be asking about that. The only problem with asking about the whys and hows of Gauss's law is it really isn't necessary, since its so obvious; akin to trying to extract information out of 1+1=2. You add a single thing with a single thing, and get two single things. An electric field diverges only from a place where charge exists. Same thing. It's tautological.