Static Electricity & Electric Fields [Physics only]

Static charge

• When certain insulating materials are rubbed together they become electrically charged: electrons are rubbed off one material and on to the other
• The material that gains electrons becomes negatively charged; the material that loses electrons is left with an equal positive charge
• Only electrons move. Protons stay in the nucleus; positive charge is never transferred
• Charged objects exert a force on each other without touching: a non-contact force. Like charges repel; unlike charges attract
• Evidence: a charged rod attracts small pieces of paper; two charged balloons hung together push apart; hair stands up when charged, each hair repelling the others
• Sparking: if enough charge builds up, the potential difference between the object and earth becomes large enough for electrons to jump across the air gap as a spark, to earth or to a nearby object