Question

Electric potential of earth, why?

Answer 1

There is a redistribution of the electrical charge in clouds. The positive charge is collected at the top of clouds and the negative - below. As a result of thunderstorms the Earth takes this negative charge due to lightings and rain. Also dust storms, volcanic eruptions and other phenomena play the role. Also discharge of the Earth has place because of the atmospheric currents observed in sunny areas. As a result, there is a certain equilibrium charge on the Earth surface.