Electric Charge

• Electric Charge:

  • When certain insulating materials are rubbed against each other they become electrically charged
  • This is called charging by friction
  • The charges remain on the insulators and cannot immediately flow away
  • One becomes positive and the other negative
• An example of this is a plastic or polythene rod being charged by rubbing it with a cloth

  • Both the rod and cloth are insulating materials
• A polythene rod may be given a charge by rubbing it with a cloth:

  
• • This occurs because negatively charged electrons are transferred from one material to the other
  • The material, in this case, the rod, loses electrons
  • Since electrons are negatively charged, the rod becomes positively charged
  • As a result, the cloth has gained electrons and therefore is left with an equal negative charge
• Charge & Electrons:

  • All objects are initially electrically neutral, meaning the negative (electrons) and positive charges are evenly distributed
  • However, when the electrons are transferred through friction, one object becomes negatively charged and the other positively charged
  • The object to which the electrons are transferred becomes negatively charged
  • The object from which the electrons leave becomes positively charged
• • This difference in charges leads to a force of attraction between itself and other objects which are also electrically neutral, by attracting the opposite charge to the surface of the objects they are attracted to
  • In the example below, when the cloth and rod are rubbed together, the electrons are transferred to the cloth and leave from the rod
• Electrons are rubbed onto the cloth leaving the cloth negatively charged and the rod positively charged: