Question

In your own words the basic idea of Gauss's law for electricity and
explain why Gauss' law is applicable but not useful to find the electric field
from a cubical charge distribution.

Why can Gauss’s law for magnetism can always be taken as
∮⃗B⋅ ⃗ da=0
.

Answer 1

(A) Gauss law for electricity why Gauss' law is applicable but not useful to find the electric field
from a cubical charge distribution.

So we see that when we assume cubical Gaussian surface around a change Q then we have a difficult integration which is not easy to solve. So for simplicity we Spherical or cylindrical surface.

(B)Gauss law for Magnetism

Magnet exist as a dipole means North pole always come with South pole so that magnetic field line is continuous.

So if we assume a Gaussian surface that no of line enter equal to no of magnetic line exit. So that net magnetic flux through closef surface is Zero.