Discuss some points about Gauss’s law.
$(i)$ The total charge contained in the closed surface is zero, then the net electric flux through a closed surface is zero.
$(ii)$ Gauss's law is true for any closed surface, no matter what its shape or size.
$(iii)$ The charges may be located anywhere inside the surface.
$(iv)$ In the situation when the surface is so chosen that there are some charges inside and some outside the electric field, whose flux appears on the left side of Equ : $\phi=\frac{\Sigma q}{\epsilon_{0}}$ is due to all the charges both inside and outside S. The term $q$ on the right side of Gauss's law, however, represents only the total charge inside S.
$(v)$ The surface that we choose for the application of Gauss's law is called the Gaussian surface.
$(vi)$ Gauss's law is often useful towards a much easier calculation of the electrostatic field when the system has some symmetry.
$(vii)$ Gauss's law is based on the inverse square dependence on distance.
Gauss’s law should be invalid if
A point charge $+Q$ is positioned at the centre of the base of a square pyramid as shown. The flux through one of the four identical upper faces of the pyramid is
In $1959$ Lyttleton and Bondi suggested that the expansion of the Universe could be explained if matter carried a net charge. Suppose that the Universe is made up of hydrogen atoms with a number density $N$, which is maintained a constant. Let the charge on the proton be :
${e_p}{\rm{ }} = - {\rm{ }}\left( {1{\rm{ }} + {\rm{ }}y} \right)e$ where $\mathrm{e}$ is the electronic charge.
$(a)$ Find the critical value of $y$ such that expansion may start.
$(b)$ Show that the velocity of expansion is proportional to the distance from the centre.
A hollow cylinder has a charge $q$ coulomb within it. If $\phi$ is the electric flux in units of $volt-meter$ associated with the curved surface $B,$ the flux linked with the plane surface $A$ in units of $V-m$ will be
What will be the total flux through the faces of the cube as in figure with side of length $'a'$ if a charge $'q'$ is placed at ?
$(a)$ $C$ $:$ centre of a face of the cube.
$(b)$ $D$ $:$ midpoint of $B$ and $C$.