Question about coulomb's force.

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To achieve maximum Coulomb's repulsion between two charges, "Q-q" and "q", one must differentiate the expression for the force between the charges with respect to "q" and set the derivative to zero. This mathematical approach identifies the condition for maximum force, as it determines the optimal distribution of charge. The discussion emphasizes the importance of understanding the relationship between "Q" and "q" in this context. Clarification was sought on why differentiation is necessary and whether to differentiate with respect to "Q" or "q". Ultimately, the inquiry was resolved, confirming the correct method for finding the maximum repulsion condition.
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1. A certain charge "Q" is to be divided into two parts, "Q-q" and "q". What is the relation of "Q" to "q" if two parts, placed at a given distance apart, are to have the maximum coulomb's repulsion?

I am unable to find the condition when there is a maximum Coulomb's repulsion. Any help will be greatly appreciated.

Thanks in Advance

DIMSKK
 
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Write down the expression for the force between the charges. Find the differentiation with respect to q and equate it to zero. That gives you the condition for the maximum coulomb's repulsion.
 
rl.bhat said:
Write down the expression for the force between the charges. Find the differentiation with respect to q and equate it to zero. That gives you the condition for the maximum coulomb's repulsion.

Why find the differentiation with respect to q and then equate it to 0? I mean why force will be maximum when we do this? Can anyone explain? Moreover, whether we differentiate the expression with "Q" or "q"?
 
Last edited:
Now I have found what is the reason. Thank you very much for help rl.bhat.
 

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