Electrostatics term 1

• Electron mass


  9,11 x 10-31 kg
• A charged object can also be attracted to a neutral conductor because of the movement of charges in the conductor
• A charged object can also be attracted to an insulator because of the movement of polarised molecules present in the insulator
• Like charges


  Exert REPULSIVE forces on each other
• Opposite charges


  Exert ATTRACTIVE forces on each other
• Charge quantisation


  All charges in the universe consist of an integer multiple of the charge of an electron
• Calculating the number of electrons gained or lost by a charge

  • +4.5 nC loses 2.81 x 10^10 electrons
  • 9 μC gains 5.63 x 10^13 electrons
• Friction (tribo-electric charging)


  Rubbing two objects together transfers electrons from one to the other
• Contact charging


  When a charged conductor touches an identical neutral conductor, electrons are transferred to make the charge on the conductors equal
• Induction


  A method of charging whereby the objects do not touch one another
• The principle of conservation of charge states that the net charge of an isolated system remains constant during any physical process
• Two identical charges on insulated stands, +5 mC and -9 mC respectively, touch and move apart again

  • The new charge on each is -2 mC, 7 mC of charge was transferred, equivalent to 4.38 x 10^16 electrons