This teacher uses a Van de Graaff generator to build up a strong static charge in his body. As he places his hand on the machine, his entire body becomes charged, including the lightweight cups stacked on his head. Initially, the cups stay in place, but as the charge increases, they begin to repel each other due to electrostatic forces. When the smaller metallic sphere is moved, it likely alters the surrounding electric field, intensifying the repulsion. The result? The cups dramatically lift of