Four charges $2 \mu C, -3 \mu C, 4 \mu C, -4 \mu C$ and $-1 \mu C$ are enclosed by a Gaussian surface of radius $2 \ m$. The net outward flux through the Gaussian surface is (in $\mu V-m$):

The electric flux for Gaussian surface $A$ that encloses the charged particles in free space is (given $q_1 = -14\, nC$,$q_2 = 78.85\, nC$,$q_3 = -56\, nC$):

$A$ charge $q$ is placed at the centre of the open end of a cylindrical vessel. The flux of the electric field through the surface of the vessel is:

The figure shows two situations in which a Gaussian cube sits in an electric field. The arrows and values indicate the directions and magnitudes (in $N-m^2/C$) of the electric flux through the faces of the cube. What is the net charge (in the two situations) inside the cube?

$(a)$ An electrostatic field line is a continuous curve. That is,a field line cannot have sudden breaks. Why not?
$(b)$ Explain why two field lines never cross each other at any point?

$A$ charge $q$ is placed at the corner of a cube of side $a$. The electric flux through the cube is