What will happen to convection currents in the mantle if earths interior eventually cools down?

If the core were to cool completely, the planet would grow cold and dead. It also would get a little dark: Power utilities pull radiant heat from Earth's crust and use it to heat water, the steam from which powers turbines to create electricity.Cooling also could cost us the magnetic shield around the planet created by heat from the core. This shield protects Earth from cosmic radiation. The shield is created by a convection process caused by constantly moving iron. Like the planet itself, Earth's core is constantly spinning. Some scientists think it's moving even faster than the rest of the planet. The friction converts kinetic energy into electrical and magnetic energy that forms the field, which deflects harmful, charged particles emanating from the sun toward the north and south poles. Your welcome :)