The electric field near a conducting surface having a uniform surface charge density $\sigma $ is given by
$\frac{\sigma }{{{\varepsilon _0}}}$ and is parallel to the surface
$\frac{{2\sigma }}{{{\varepsilon _0}}}$ and is parallel to the surface
$\frac{\sigma }{{{\varepsilon _0}}}$ and is normal to the surface
$\frac{{2\sigma }}{{{\varepsilon _0}}}$ and is normal to the surface
A solid conducting sphere has cavity, as shown in figure. A charge $+ {q_1}$ is situated away from the centre. A charge $+q_2$ is situated outside the sphere then true statement is
Two metal spheres, one of radius $R$ and the other of radius $2R$, both have same surface charge density $\sigma $. They are brought in contact and separated. What will be new surface charge densities on them ?
A solid conducting sphere of radius $a$ has a net positive charge $2Q$. A conducting spherical shell of inner radius $b$ and outer radius $c$ is concentric with the solid sphere and has a net charge $-Q$. The surface charge density on the inner and outer surfaces of the spherical shell will be
Two spheres of radius $R$ and $2R$ having charge $Q$ and $2Q$ respectively are placed far away from each other. How much charge will flow when key $'k'$ is pressed ?
Four metal conductors having different shapes
$1.$ A sphere $2.$ Cylindrical
$3.$ Pear $4.$ Lightning conductor
are mounted on insulating stands and charged. The one which is best suited to retain the charges for a longer time is