A point charge q is placed at a vertex of a cube. Another point charge Q is placed at the body centre of the cube. If the net electric flux passing through a face that does not contain the vertex where q is placed is zero, the value of Q is :

Step-by-step solution

The flux from the charge q at the vertex into the entire cube is q 8 ₀ . This flux passes only through the 3 faces that do not meet at the vertex (the flux through the 3 faces meeting at the vertex is zero because the electric field is parallel to their surfaces). By symmetry, the flux through one such non-adjacent face is: _q = 1 3 q 8 ₀ = q 24 ₀ The charge Q at the body centre contributes symmetrically to all 6 faces of the cube. The flux through any one face due to Q is: _Q = Q 6 ₀ The net flux through the non-a