Static electricity

• Static electricity

  The build-up of charge on insulating materials that can cause sparks when discharged
• All materials contain positive protons and negative electrons
• Normally, the positive and negative charges cancel each other out, making most materials neutral overall
• Rubbing materials together

  Friction causes electrons to be rubbed off one object and onto the other
• Conducting materials

  Materials where electrons are able to move, so the transferred electrons flow back and no charge builds up
• Insulating materials

  Materials where electrons can't flow back, so the transferred electrons leave a positive static charge on the material that lost them and a negative static charge on the material that gained them
• The specific materials involved determine which way the electrons get transferred
• Only the negative electrons are transferred, the positive static charges occur because an object has lost negative charge, not because it's gained positive protons
• Charge build-up on an object

  1. As more electrons are transferred, a potential difference develops between the charged object and the earth or any earth object

  2. If the potential difference is large enough, electrons can jump across the gap, causing a spark
• Charges can sometimes build up on conductors too, like on the metal frame of a car, which can then discharge through a person touching the car, causing a small spark