A Van de Graaff generator is a device that can generate electrical charge using friction and conduction.
Design & Method
In order to understand how the Van de Graaff works, it’s first easier to understand how the underlying ‘charger’ of it works: a simple rubber belt moving across two different materials, usually glass and metal.
Essentially, we have created two, very strongly charged materials, using the rubber as medium for charge transfer. Now, what would happen if we use polarisation with two metal combs?
Now all we need to do is to connect something to these metal combs. How about two differently sized metal spheres? Due to the Electrostatic Equilibrium of conductors, the charges would move to the surface of the sphere.
And just like that, we have a Van De Graaff generator!