What is the angle between the electric dipole moment and the electric field strength due  to it on the equatorial line.......$^o$

If the charge on a capacitor is increased by $2\, C$ the energy stored in it increases by $21\%$. The original charge on the capacitor (in coulomb) is

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 ......... $pF$

Two charges $+q$ and $-3q$ are placed on $x-$ axis separated by a distance $d$. ($-3q$ is right of $q$) Where should a third charge $2q$ be placed such that it will not experience any force ?

The equivalent capacitance between $A$ and $B$ is (in $\mu\, F$)

Two identical charged spherical drops each of capacitance $C$ merge to form a single drop. The resultant capacitance