A positive 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 $\mathrm{\varphi }$. Now a hemispherical shell of the 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

The given figure gives electric lines of force due to two charges $q_1$ and $q_2$. What are the signs of the two charges?

A cylinder on whose surfaces there is a vertical electric field of varying magnitude as shown. The electric field is uniform on the top surface as well as on the bottom surface therefore, this cylinder encloses

A metallic solid sphere is placed in a uniform electric field. The lines of force follow the path(s) shown in figure as :