Gr12 charge attraction repulation question

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The discussion revolves around a question regarding the forces between two charges, initially both positive and then with one replaced by a negative charge. The confusion arises from the belief that the force must change in magnitude due to attraction or repulsion. However, it is clarified that the question focuses on the magnitude of the force, which remains the same according to Coulomb's law. The key point is that while the direction of the force changes, the magnitude does not, as the question specifically asks for the magnitude comparison. Understanding this distinction is crucial for accurately answering the question.
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I don't understand why the answer is B
It make sense if the question is asking which one is the incorrect force since my diagram contain all the arrows except B..
 
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Question:Two charges of +Q are 1 cm apart. If one of the charges is replaced by a charge of –Q, the magnitude of the force between them is
Ans: the same

Won't they either get attracted or repelled? then , the magnitude will change isn't it?
 
For the first question, you already know the forces are in directions A, C and D.
Form the vector sum of forces A and C, then compare it to the size of the force in direction D.

For the second question, just apply Coulomb's law to the 2 situations to compare the magnitudes of the forces. It doesn't ask anything about the direction.
 
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