A thin spherical conducting shell of radius $R$ has a charge $q.$ Another charge $Q$ is placed at the centre of the shell. The electrostatic potential at a point $p$ a distance $R/2$ from the centre of the shell is
$\frac{{\left( {q + Q} \right)2}}{{4\pi { \in _0}R}}$
$\frac{{2Q}}{{4\pi { \in _0}R}}$
$\frac{{2Q}}{{4\pi { \in _0}R}} - \frac{{2q}}{{4\pi { \in _0}R}}$
$\frac{{2Q}}{{4\pi { \in _0}R}} + \frac{{q}}{{4\pi { \in _0}R}}$
Force between $A$ and $B$ is $F$. If $75\%$ charge of $A$ is transferred to $B$ then force between $A$ and $B$ is
Two charged spheres of radii $R_1$ and $R_2$ having equal surface charge density. The ratio of their potential is
Charges $+q$ and $-q$ are placed at points $A$ and $B$ respectively which are at distance $2\,L$ apart, $C$ is the midpoint between $A$ and $B$ . The work done in moving a charge $+ Q$ along the semicircle $CRD$ is
Four capacitors with capacitances $C_1 = 1\,μF, C_2 = 1.5\, μF, C_3 = 2.5\, μF$ and $C_4 = 0.5\, μF$ are connected as shown and are connected to a $30\, volt$ source. The potential difference between points $B$ and $A$ is....$V$
A parallel plate capacitor with air between the plates has a capacitance of $9\ pF$. The separation between its plates is '$d$'. The space between the plates is now filled with two dielectrics. One of the dielectric has dielectric constant $K_1 = 6$ and thickness $\frac{d}{3}$ while the other one has dielectric constant $K_2 = 12$ and thickness $\frac{2d}{3}$. Capacitance of the capacitor is now........$pF$