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A point charge Q is placed at the origin. An imaginary square plate of side a is positioned in the y-z plane with its centre at the point (a/2, 0, 0). What is the total electric flux passing through this square plate?
- Q / (8*epsilon0)
- Q / (4*epsilon0)
- Q / (6*epsilon0)
- Q / (2*epsilon0)
Correct answer: Q / (6*epsilon0)
Solution
The square plate (side a, centred at (a/2, 0, 0)) is equivalent to one face of a cube of side a centred at the origin. By Gauss's law, total flux through the complete cube = Q/epsilon0. By symmetry, flux through each of the 6 faces is equal, so flux through the square = Q/(6*epsilon0).
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