Question

using Gauss's law, obtain the electric flux due to a point charge 'q' enclosed in a cube of side 'a'.

Answer 1

According to Gauss theorem,
Electric flux is the ratio of charge inclosed inside the Gaussian surface to permittivity of medium . e.g., Ф = Q/ε₀

Here you can see , charge Q inclosed inside the Gaussian surface { e.g., cubical}
Hence, electric flux , Φ = q/ε₀