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Question
The sum of all electromagnetic forces between different particles of a system of charged particles is zero
Options
only if all the particles are positively charged
only if all the particles are negatively charged
only if half the particles are positively charged and half are negatively charged
irrespective of the signs of the charges
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Solution
irrespective of the signs of the charges.
The sum of all electromagnetic forces between different particles of a system of charged particles is zero irrespective of the sign of the charges, because electromagnetic force is a vector quantity that depends upon the direction. So, we consider the directions while adding vector quantities.
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