Two point charges 2q and q are placed at the vertex A and at the centre of the face CDEF of a cube as shown in the figure [cube with top face ABCD and bottom face HGFE, with 2q sitting on the corner A and q at the centre of the side face CDEF]. The electric flux passing through the cube is

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Accepted Answer

(3) (3q)/(4ε₀). A charge sitting at a corner is shared by eight identical cubes, so only 1/8 of its flux passes through this one: φ₁=1/8·(2q)/(ε₀)=q/(4ε₀). A charge sitting on a face is shared by the two cubes on either side of that face, so half of its flux enters this cube: φ₂=1/2·q/(ε₀)=q/(2ε₀). Total: φ=q/(4ε₀)+q/(2ε₀). φ=(3q)/(4ε₀).

Two point charges 2q and q are placed at the vertex A and at the centre of the face CDEF of a cube as shown in the figure [cube with top face ABCD and bottom face HGFE, with 2q sitting on the corner A and q at the centre of the side face CDEF]. The electric flux passing through the cube is

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