What is the flux through a cube of side 'a' if a point charge of q is at one of…

4 2012 AIPMT-PRE Electric Charges and FieldsGauss's law Medium
What is the flux through a cube of side 'a' if a point charge of q is at one of its corner?
A $\frac{q}{2\varepsilon_0}6a^2$
B $\frac{2q}{\varepsilon_0}$
C $\frac{q}{8\varepsilon_0}$
D $\frac{q}{\varepsilon_0}$

Detailed Solution

A charge at a corner is shared equally by 8 cubes that meet at that corner.
By Gauss's theorem the total flux from the charge is $\frac{q}{\varepsilon_0}$.
Flux through one cube $= \frac{1}{8}\times\frac{q}{\varepsilon_0} = \frac{q}{8\varepsilon_0}$

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