If two infinite plane sheets having same surface charge density $\sigma$ are placed parallel to each other,then the electric field between the two sheets is . . . . . . .

$A$ solid metallic sphere has a charge $+3 Q$. Concentric with this sphere is a conducting spherical shell having charge $-Q$. The radius of the sphere is $A$ and that of the spherical shell is $B$ $(B > A)$. The electric field at a distance $R$ $(A < R < B)$ from the centre is $(\varepsilon_0 = \text{permittivity of vacuum})$

$A$ hollow spherical shell of radius $r$ has a uniform charge density $\sigma$. It is kept in a cube of edge $3r$ such that the centres of the cube and the shell coincide. Then the electric flux coming out of one face of a cube is ($\varepsilon_0$ - permittivity of free space).

Consider two infinitely large plane parallel conducting plates as shown below. The plates are uniformly charged with a surface charge density $+\sigma$ and $-2 \sigma$. The force experienced by a point charge $+q$ placed at the midpoint between the two plates will be:

The electric field at a distance $r$ from the centre in the space between two concentric metallic spherical shells of radii $r_1$ and $r_2$ carrying charges $Q_1$ and $Q_2$ respectively is $(r_1 < r < r_2)$.

Obtain the expression for the electric field due to a uniformly charged spherical shell at a point outside it.