well, lemme ask you...how wud a charge know of presence of another charge ???......
every charge sets up an electric field to know the presence of other chages so that they can interact with each other...
.....a quantity that does not depend on magnitude of the charge wud help making problems simpler than ever....and that's what hidden behind this concept....
hope it helps...cheero :)
Who says nothing is impossible.
I've been doing nothing for years !!..............
I know KUNG FU KARATE
and 47 other dangerous words.............