Draw electric field lines of positive charge.

A charge is kept at the central point $P$ of a cylindrical region. The two edges subtend a half-angle $\theta$ at $P$, as shown in the figure. When $\theta=30^{\circ}$, then the electric flux through the curved surface of the cylinder is $\Phi$ If $\theta=60^{\circ}$, then the electric flux through the curved surface becomes $\Phi / \sqrt{n}$, where the value of $n$ is. . . . . . .

A charge $Q$ is fixed at a distance $d$ in front of an infinite metal plate. The lines of force are represented by

A charge $Q\;\mu C$ is placed at the centre of a cube, the flux coming out from any surfaces will be

Electric charge is uniformly distributed along a long straight wire of radius $1\, mm$. The charge per $cm$ length of the wire is $Q$ $coulomb$. Another cylindrical surface of radius $50$ $cm$ and length $1\,m$ symmetrically encloses the wire as shown in the figure. The total electric flux passing through the cylindrical surface is

Write Gauss’s law and give its expression.