Two point charges $q_1 = 6\ \mu\text{C}$ and $q_2 = 4\ \mu\text{C}$ are kept at points A and B in air where distance $AB = 10$ cm. What is the increase in potential energy of the system when $q_2$ is moved towards $q_1$, by 2 cm ? $\left(\dfrac{1}{4\pi\epsilon_0} = 9 \times 10^9\ \text{SI units}\right)$

For a uniformly charged plane sheet, the variation of electric field (E) with distance (d) is correctly shown graphically in graph

A point charge 'Q' is placed at the centre of the line joining two equal charges '+q' and '+q'. The value of 'Q' when the system is in equilibrium is

The number of lines of force originating from a point charge of $2 \times 8.85 \times 10^{-9}$ C in a medium of dielectric constant $10$ is ($\epsilon_0 = 8.85 \times 10^{-12}$ SI unit)