A given charge situated at a distance $r$ from an electric dipole on it axis experiences a force $F$. If the distance of the charge from the dipole is doubled, the force acting on the charge will be

What is the effective capacitance between points $X$ and $Y$ ?......$\mu F$

Condenser Ahas a capacity of $15\  \mu F$ when it is filled with a medium of dielectric constant $15$. Another condenser $B$ has a capacity $1\  \mu F$ with air between the plates. Both are charged separately by a battery of $100\,V$ . After charging, both are connected in parallel without the battery and the dielectric material being removed. The common potential now is.......$V$

Two identical charged spheres suspended from a common point by two massless strings of length $l$ are initially a distance $d(d  << I) $ apart because of their mutual repulsion. The charge begins to leak from both the spheres at a constant rate. As a result charges approach each other with a velocity $v$. Then as a function of distance $x$ between them,

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........$pF$

An electric dipole of dipole moment $\vec P$ is lying along a uniform electric field $\vec E$ . The work done in rotating the dipole by $90^o$ is