Umre_afis - charges, then, this plane is an equipotential...

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PHYS 102 - QUIZ-3 SOLUTION The potential (relative to a point at infinity) midway between two charges of equal magnitude and opposite sign is zero. Is it possible to bring a test charge from infinity to this midpoint in such a way that no work is done in any part of the displacement? If so, describe how it can be done. If it is not possible, explain why. Answer: q L It is given that the potential at the midway is 0. This means that no net work is done when a test charge is brought from infinity to this midway. The question asks if it is possible to bring a test charge from infinity to this midway such that no work is done IN ANY PART of the displacement. If we draw a plane P such that - every point on it have the same distance to two charges and, - it passes through midway point and, - it is perpendicular to the line connecting the two
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Unformatted text preview: charges, then, this plane is an equipotential surface that extends to infinity. That is, at any point on plane P, the potential will be zero. Assume a test charge q on plane P and that resides at infinity. If we move q over plane P (it does not have to be a line, it can be in any direction on plane P such as the one shown in figure) and bring it to midway point, then in ANY part of the displacement no work will be done. Therefore, it is possible to bring a test charge from infinity to zero-potential midway without doing ANY work at ANY part of the displacement. { To students who claimed electric field requires us to do some work : Since equipotential surfaces are perpendicular to E electric field lines, it does no work on the equipotential surface.} +Q − Q...
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