Two point charges $+10 \mu \mathrm{C}$ and $4 \mu \mathrm{C}$ are placed 10 cm apart in air. The work required to be done to bring them 2 cm closer is

$$ \left(\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \text { SI units }\right) $$

Out of the following molecules the one which represents the polar molecule is

The electric field intensity near a conducting surface having uniform surface charge density ' $\sigma$ ' is given by ( $\varepsilon_0=$ permittivity of free space)

A regular hexagon of side 6 cm has a charge of $2 \mu \mathrm{C}$ at each of its vertices, what is the potential at the centre of the hexagon?

$$ \left[\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \text { SI unit }\right] $$