A point charge Q is placed at the corner of a square of side a. Find the flux through the square.

Explanation

The electric field due to Q at any point on the square will be along the plane of the square and perpendicular to the area vector`(vecA)`. As `phi = vec( E ) * vec(A)` and `vec E _|_vecA`, hence `phi =0`. In other words, we can say that no line is crossing the square and so flux is 0.
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