A charge $Q$ is placed at a distance of $4R$ above the centre of a disc of radius $R.$ The magnitude of flux through the disc is $\varphi .$ Now a hemispherical shell of radius $R$ is placed over the disc such that it forms a closed surface. The flux through the curved surface (taking the direction of area vector along outward normal as positive), is -

Gauss law is given by ${\in }_0\oint \overrightarrow{E}.\overrightarrow{ds}=q,$ if net charge enclosed by Gaussian surface is zero then-.

The fig. shows lines of constant potential in a region in which an electric field is present. The value of the potential are written in brackets of the points $A, B$ and $C,$ the magnitude of the electric field is greatest at the point -

The figure shows a thick metallic sphere. If it is given a charge $+Q,$ then an electric field will be present in the region