Static Electricity

• Static electricity is the build up of charge on insulating materials and can cause sparks when discharged
• All materials contain charge because they contain positive protons and negative electrons. Normally these charges cancel each other out, leaving the objects neutral overall. If materials are rubbed together though then the friction between the two objects causes the electrons from one to be transferred to the other object.
• In conducting materials the electrons will flow straight back again so no charge ever builds up. But in insulating materials like a polythene rod and cloth the electrons can't flow back so each object will have either a negative or positive charge. Which way the electrons are transferred depends on the specific materials involved.
• If an object keeps gaining negative electrons and the size of the charge increases, a potential difference will occur between the object and any earthed object. If the potential difference is large enough, the electrons can jump across the gap. This a spark.
• Charges can build up on conductors it is just much less common.