Coulomb's Law And Superposition

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Three equal positive charges sit at the corners of an equilateral triangle, and a student wants the net force on any one charge, so which direction does it point?

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The principle of superposition states that the net force on a charge is the vector sum of the individual Coulomb forces from every other charge acting independently. Consider the top charge: the two lower charges each repel it, and by symmetry the horizontal components of these two repulsions cancel while the vertical components add. The resultant therefore points straight away from the midpoint of the opposite side, which is the same as pointing radially outward along the line joining the centroid to that charge. Because all three charges and distances are identical, this symmetry holds for every corner. The option pointing toward the centroid is wrong because equal positive charges repel, not attract, so the force cannot point inward. The option along one side only is wrong because it ignores the contribution of the second neighbouring charge. The option claiming zero net force is wrong because the two repulsive forces are not anti-parallel and cannot cancel. As described in NCERT Class 12, Chapter 1 (Electric Charges and Fields), superposition allows adding forces vectorially. A direction check confirms outward repulsion is consistent with three like charges pushing each other apart symmetrically.

Coulomb's Law And Superposition

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