In Millikan's oil drop experiment an oil drop carrying a charge $Q$ is held stationary by a potential difference $2400\,V$ between the plates. To keep a drop of half the radius stationary the potential difference had to be made $600\,V$. What is the charge on the second drop

The electrostatic potential inside a charged spherical ball is given by $\phi= a{r^2} + b$ where $r$ is the distance from the centre and $a, b$ are constants. Then the charge density inside the ball is:

The potential function of an electrostatic field is given by $V = 2x^2$. Determine the electric field strength at the point $(2\,m, 0, 3\,m)$

If the electric potential at any point $(x, y, z) \,m$ in space is given by $V =3 x ^{2}$ volt. The electric field at the point $(1,0,3) \,m$ will be ............

The electric potential at a point in free space due to charge $Q$ coulomb is  $V=Q$$ \times {10^{11}}\,V$ . The electric field at that point is 

The electric potential at a point $(x, y, z)$ is given by $V=-x^2y-xz^3 +4 $. The electric field at that point is