Two concentric conducting thin spherical shells $A$ and $B$ having radii ${r_A}$ and ${r_B}$ (${r_B} > {r_A})$ are charged to ${Q_A}$ and $ - {Q_B}$$(|{Q_B}|\, > \,|{Q_A}|)$. The electrical field along a line, (passing through the centre) is
A charge $Q$ is uniformly distributed over a large square plate of copper. The electric field at a point very close to the centre of the plane is $10\, V/m$. If the copper plate is replaced by a plastic plate of the same geometrical dimensions and carrying the same charge $Q$ uniformly distributed, then the electric field at the point $P$ will be......$V/m$
A positive charge $q$ is placed in a spherical cavity made in a positively charged sphere. The centres of sphere and cavity are displaced by a small distance $\vec l $ . Force on charge $q$ is :
Obtain the expression of electric field by charged spherical shell on a point outside it.
An electrostatic field in a region is radially outward with magnitude $E$ = $\alpha r$ , where $\alpha $ is a constant and $r$ is radial distance. The charge contained in a sphere of radius $R$ in this region (centred at the origin) is
An infinitely long solid cylinder of radius $R$ has a uniform volume charge density $\rho$. It has a spherical cavity of radius $R / 2$ with its centre on the axis of the cylinder, as shown in the figure. The magnitude of the electric field at the point $P$, which is at a distance $2 \ R$ from the axis of the cylinder, is given by the expression $\frac{23 \rho R }{16 k \varepsilon_0}$. The value of $k$ is