# Homework Help: Coulomb's Law.

1. Aug 24, 2009

### supreabajaj

Coulomb's Law........

Can anyone please tell me why is Coulomb's Law applicable only to the point charges?

2. Aug 24, 2009

### kuruman

Re: Coulomb's Law........

Write down Coulomb's Law. What do the symbols in the equation mean?

3. Aug 24, 2009

### supreabajaj

Re: Coulomb's Law........

Statement- The electrostatic force of interaction between any two point charges is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them.

Mathematical Expression- F=Kq1q2/r*r

4. Aug 24, 2009

### Pinu7

Re: Coulomb's Law........

Let us consider an extended body having a charge(known as charge density). We could approximate by assuming that the extended body is made out of many point-like charges(more point like charges=better approximation).

Then consider another charged body(pointlike or non pointlike. for simplification, try point-like). Then, apply Couloumb's law through summation.

Then take the limit and see what happens.

5. Aug 24, 2009

### kuruman

Re: Coulomb's Law........

There is your answer. Coulomb's Law, the way you have written it, involves two charges and two charges only. But if you know how to write the force between two charges, you can find the force between charge distributions by assembling forces in pairs, but that's not Coulomb's Law, but an application of it.