The electric field and the potential of an electric dipole vary with distance $$r$$ as

Two tiny spheres carrying charges $$1.8 \mu \mathrm{C}$$ and $$2.8 \mu \mathrm{C}$$ are located at $$40 \mathrm{~cm}$$ apart. The potential at the mid - point of the line joining the two charges is

Electric field due to infinite, straight uniformly charged wire varies with distance $$r$$ as

A $$2 \mathrm{~g}$$ object, located in a region of uniform electric field $$\mathrm{E}=\left(300 \mathrm{NC}^{-1}\right) \hat{\mathbf{i}}$$ carries a charge $$Q$$. The object released from rest at $$x=0$$, has a kinetic energy of $$0.12 \mathrm{~J}$$ at $$x=0.5 \mathrm{~m}$$. Then, $$Q$$ is