Two point charges 2q and q are placed at vertex A and centre of face CDEF of the cube as shown in figure. The electric flux passing through the cube is :

Question

G1 Physics · Accepted Answer

Use Gauss's law by determining the fraction of each boundary charge that belongs to the cube. The charge 2q is placed at a vertex of the cube. Eight identical cubes can be assembled around a vertex, so the effective enclosed contribution from this charge is (2q)/8 = q/4. The charge q is placed at the centre of a face. Two identical cubes can be joined across that face, so its effective enclosed contribution is q/2. Therefore the total effective enclosed charge is Q(enclosed) = q/4 + q/2 = 3q/4.…