A Shocking Experience

A Van de Graaf generator is a common laboratory device used to build up high voltages.

A motor driven INSULATING belt (D) inside the generator moves past a comb like set of metal needles (F) which are maintained at a high voltage. A continuous supply of ELECTRONS is deposited on the belt which is then carried up into the hollow metal sphere (A).

Because of mutual repulsion, the ELECTRONS move to the outer surface of the sphere enabling the inside surface to receive more ELECTRONS from the belt.

Effect of Humidity on VDG  If it is a humid day then there are a lot of water molecules in the air.  The water molecules can come into contact with the surface of the metal dome taking away some of the built up charge.  Meaning that on a humid day a Van de Graaf generator would be difficult to use.

An object which gains a static CHARGE doesn’t hold the charge forever. Electrons tend to move, returning the object to its NEUTRAL condition. When a negatively charged object and a positively charged object are brought together, electrons move until both objects have the same CHARGE.

The transfer of static electricity as electric charges move off an object is called static CURRENT.

How did we avoid electrocution? #1 Special stool The stool is made of insulating material. This means that it doesn’t transfer electrons very well. More dangerous would be if the person was standing directly on the ground which gives an easy path for electrons to follow.

How did we avoid electrocution? The Van de Graaf generator illustrates static electricity (stationary electricity) meaning that the electrons are stationary on the dome. The electricity in your home or in the electric chair is moving electricity... the more dangerous kind.