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Electricity > Static Charge

At around 600BC, an ancient Greek philosopher reported that if a piece of animal fur is rubbed over the surface of a piece of amber a 'charge' could be accumulated. He noticed that this charge could attract other objects like hair and if rubbed for a long time sparks could me made. The ancient Greek word for amber is 'elektron' and forms the basis for the words electricity and electrostatics that are used today to describe the phenomenon.

Electric currents happen when forces make charges move in a circuit. When an electric charge cannot move, it can create large forces on objects around it.

If you take a duster and polythene rod and rub them together for long enough, both become charged. The polythene rod takes electrons from the duster and so becomes negatively charged. Because the rod takes the negative charges away, the duster becomes positively charged. Both the duster and rod will exert forces on other objects that are uncharged. Hairs, tissue paper pieces and polystyrene balls will be attracted towards both charged objects.

The same can be achieved by rubbing a balloon on your hair or a duster.

Van De Graff generators use the same method to build up a massive static charge which is insulated from the base and therefore earth. Discharging this static charge usually results in a large spark jumping between the dome of the Van De Graff and the earthed object.

Fig 1 (below) shows how both objects become charged.

Fig 1: Static Charge
Fig 1:
Static Charge

If the two objects have different charges then they will attract each other. If both have the same charge, they will repel.