Let us assume that the charge q = ± 10 μC = 10–5 C is placed at a distance of 5 cm from the square ABCD of each side 10 cm. The square ABCD can be considered as one of the six faces of a cubic Gaussian surface of each side 10 cm.
Now, the total electric flux through the faces of the cube as per Gaussian theorem
Therefore, the total electric flux through the square ABCD will be