Electrostatics

A disk of radius \({a \over 4}\) having a uniformly distributed charge 6C is placed in the xy-plane with its centre at (\(-\)a/2, 0, 0). A rod of length a carrying a uniformly distributed charge 8C is placed on the x-axis from x = a/4 to x = 5a/4. Two points charges \(-\)7C and 3C are placed at (a/4, \(-\)a/4, 0) and (\(-\)3a/4, 3a/4, 0), respectively. Consider a cubical surface formed by six surfaces \(x=\pm a/2,y=\pm a/2,z=\pm a/2\). The electric flux through this cubical surface is