 Solution

ID: past-exam-of-the-physics-2-paper-of-the-university-of-oxford/2017/4/i/solution

The six faces subtend equal solid angles at the central point charge. Gauss's law fixes their total outward electric flux at

q / ϵ_{0}

Φ_{each face} = \frac{q}{6 ϵ _{0}} .

For negative

q

the same signed expression represents inward electric flux. The result is independent of the side length.

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