Electric Charge...

Two non-conducting plates $$A$$ and $$B$$ of radii $$2R$$ and $$4R$$ respectively are kept at distances $$x$$ and $$2x$$ from the point charge $$q$$. A surface cutout of a non conducting shell $$C$$ is kept such that its centre coincides with the point charge. Each plate and the spherical surface carries a surface charge density $$\sigma$$. If $$\phi_{1}$$ is flux through surface of $$(B)$$ due to electric field of $$(A)$$ and $$\phi_{2}$$ be the flux through $$(A)$$ due to electric field of $$(B)$$ then:

A point charge $$Q(C)$$ is placed at the origin. Find the electric flux of which  an area $$4\pi\ m^2$$ on a concentric spherical shell of radius $$R$$ 

Force$$ = F,$$ When a dielectric rod is placed between charges as shown. new force

Two similar very small conducting spheres having charges $$40\,\mu C$$ and $$ - 20\,\mu C$$ are some distance apart. Now they are touched and kept at the same distance. The ratio of the initial to the final force between them is:

Three point charges $${q_1},{q_2}$$ and $${q_3}$$ are taken such that when $${q_1}$$ and $${q_2}$$ are placed close together to form a single point charge, the force on $${q_3}$$ at distance $$L$$ from this combination is a repulsion of $$2$$ unit magnitude. When $${q_2}$$ and $${q_3}$$ are combined, the force on $${q_1}$$, from same distance $$L$$ is of magnitude $$4$$ unit and is attractive. Also $${q_3}$$ and $${q_1}$$ combining exert $$6$$ a force of magnitude $$18$$ unit attractive on $${q_2}$$ from same distance $$L$$, Algebraic ratio of charges $${q_1}, {q_2}$$ and $${q_3}$$ is:

The flux of the electric field due to charges distributed in a sphere of radius $$5$$ cm is $$10$$ Vm. What will be the electric flux, through a concentric sphere of radius $$10$$ cm ?

The electric flux emerging through the closed surface $${S_1}$$ shown in figure which intersects the spherical conductor $$S,$$ due to the presence of a positive charge very near to conductor is:

A number of spherical conductors of different radii are changed to same potential. The surface charge density of each conductor is related with its radius as

Three infinitely charged sheets are kept parallel to $$x-y$$ plane having charge densities as shown. Then the  value of electric field at $$'P'$$ is:

Two point charges placed at a distance r in air expert a force F on each other. The value of distance R at which they experience force $$4F$$ when placed in a medium of dielectric constant $$K = 16$$ is: