Question

A point charge +100nC is at a distance 2mm directly the Centre of a square of side 5cm of a cube. What is the magnitude of electric flux through the sphere

Answer 1

Answer:

Explanation:

Approximately half of the flux through a closed surface enclosing the charge.

Imagine the closed surface to be a spherical surface just touching the corners of the given square. Assume the given square to be in the horizontal plane (as per the question).

Consider a vertical section through the centre of the sphere with a diagonal of the square as a chord. If we calculate the radius of the section (and the sphere) we find that it is approximately half the diagonal of the square, which is to be expected since the charge is just 2 mm above the square.

The rest follows.

Edit: Earlier that was “If we calculate the diameter of the section”. I think that should have been “radius”, now corrected.

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