Principle: We know that the capacity of a uniformly charged hollow spherical conductors is $$C=4 \pi \varepsilon_{0} R$$ Obviously, for the capacity to be large the radius $$R$$ should be large. Further at the pointed ends of a charged conductor, the surface density of charge (i.e., charge/area) is more as compared to any plane surface, therefore the electric field near the pointed ends of the conductor is stronger than at any other places. The working of the Van-de Graff generator is based on these facts.
Uses:
(i) To generate high voltage.
(ii) To accelerate $$\alpha$$ particles, protons, and deuterons, etc in nuclear disintegration.
(iii) Disadvantage: Due to its large size it is not convenient to carry it from one place to another.