Van de Graaff generators produce strong electric fields by using a moving belt to transfer charge to a conductive sphere, increasing its voltage. They can generate over 20 million volts with pressurized gas. Electric fields are regions of space around charged objects where other charges experience a force. The strength of the electric field depends on the magnitude of the charge and distance from it. Conductors allow the redistribution of charge on their surfaces, shielding their interiors from electric fields.