Demonstrating Electric Charges (CIE IGCSE Physics)

• Electrostatic repulsion is caused by the force between charges
  • When these charges are the same as each other, they repel (push apart)
• In simple experiments showing the production of electrostatic charges by friction, insulating solids such as plastics are given a charge
  • This is done using friction to transfer electrons from the surface
• By removing electrons, which have negative charge, the insulator is left with a positive charge

Method:

• Suspend one of the insulating materials using a cradle and a length of string so that the material can rotate freely
• Rub one end of the material using a cloth (in order to give it a charge)
• Now take a second piece of insulating material and charge that by rubbing with a cloth
• Hold the charged end of the second piece close to the charged end of the first piece:
  • If the first piece rotates away (is repelled) from the second piece then the materials have the same charge
  • If the first piece moved towards (is attracted to) the second piece then they have opposite charges