Van de Graaff generator
Other electrostatic machines like the Wimshurst machine or Bonetti machine work similarly to the Van De Graaff; charge is transported by moving plates, disks, or cylinders to a high voltage electrode. For these generators, however, corona discharge from exposed metal parts at high potentials and poorer insulation result in smaller voltages. In an electrostatic generator, the rate of charge transported (current) to the high-voltage electrode is very small. After the machine is started, the voltage on the terminal electrode increases until the leakage current from the electrode equals the rate of charge transport. Therefore, leakage from the terminal determines the maximum voltage attainable. In the Van de Graaff generator, the belt allows the transport of charge into the interior of a large hollow spherical electrode. This is the ideal shape to minimize leakage and corona discharge, so the Van de Graaff generator can produce the greatest voltage. This is why the Van de Graaff design has been used for all electrostatic particle accelerators. In general, the larger the diameter and the smoother the sphere is, the higher the voltage that can be achieved.
Gaston Planté
Planté also investigated the differences between static electricity and dynamic electricity (i.e., from batteries). As part of this investigation, Planté invented a mechanical device that he called the Rheostatic Machine. The Rheostatic Machine used a bank of mica capacitors, a clever rotating commutator, and a series of contacts to alternately charge a bank of capacitors in parallel (from a high-voltage battery source) and then connect the capacitors in series. This arrangement multiplied the battery voltage by the number of capacitor stages to obtain very high voltages. By rapidly rotating the shaft, a series of high-voltage sparks many centimetres long could be rapidly generated. This device was a mechanical predecessor of the modern-day Marx generator. Using this device, Planté explored the electrical breakdown of air, the formation of Lichtenberg figures, and the behaviour of thin wires when pulsed by high electric currents.