If $\oint_s \vec{E} \cdot \overrightarrow{d S}=0$ over a surface, then:
the electric field inside the surface is necessarily uniform.
the number of flux lines entering the surface must be equal to the number of flux lines leaving it.
the magnitude of electric field on the surface is constant.
all the charges must necessarily be inside the surface.
Figure shows electric field lines due to a charge configuration, from this we conclude that
A charge $Q$ is placed at a distance $a/2$ above the centre of the square surface of edge $a$ as shown in the figure. The electric flux through the square surface is
How does the electric field lines depend on area ?
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
An electric field $\overrightarrow{\mathrm{E}}=4 \mathrm{x} \hat{\mathrm{i}}-\left(\mathrm{y}^{2}+1\right) \hat{\mathrm{j}}\; \mathrm{N} / \mathrm{C}$ passes through the box shown in figure. The flux of the electric field through surfaces $A B C D$ and $BCGF$ are marked as $\phi_{I}$ and $\phi_{\mathrm{II}}$ respectively. The difference between $\left(\phi_{\mathrm{I}}-\phi_{\mathrm{II}}\right)$ is (in $\left.\mathrm{Nm}^{2} / \mathrm{C}\right)$