# Definition of Coulomb's law

In the article about Coulomb's law

There is following sentence:

Coulomb's law is an experimental law of physics that calculates the amount of force between two electrically charged particles at rest.

However in the Griffith's Introduction to electrodynamics

Introduction before explaining Coulomb's Law, there is following sentence:

To begin with, we shall consider the special case of electrostatics in which all the source charges are stationary (though the test charge may be moving).

What i'm confusing is: Wikipedia applies to two charges at rest but Griffith's book applies to stationary source charge.

They collide with each other. Which is correct one?

• The sentence in parentheses explains that stationary is equivalent to being at rest. No collision at all :-) Commented Nov 4, 2023 at 16:25

Both statements are correct.

Wikipedia description and Griffiths are saying the same thing: in electrostatics, the charges we're talking about are not moving. But Griffiths adds a little twist by mentioning that the charge we use to "test" or "measure" things can be moving. He's just setting the stage for stuff he'll talk about later in the book.

• But wikipedia says that the two charges must be at rest to apply coulomb's law, while Griffiths says test charge can move. How both are correct?
– KHJ
Commented Nov 4, 2023 at 16:38
• @KHJ I believe Alex is probably right (though it would help to see Griffiths statement in context). If the charges were moving Coulomb's law wouldn't cover the additional magnetic forces associated with moving charges. Commented Nov 4, 2023 at 16:53
• Then can i think Griffths is correct and wikipedia is also correct because Griffiths include the situation which wikipedia says?
– KHJ
Commented Nov 4, 2023 at 16:57