electrical energy

• power


  tells us how much energy is transferred per second (w)
• fuses

  • attaches to a plug
  • inside the fuse is a tiny wire which will melt if the current gets too big
  • this will break the circuit and stop electricity from flowing
• AC - alternating current

  • from mains electricity and most generators
  • when current continually changes direction
  • caused by a voltage that changes from max positive to max negative
• DC - direct current

  • flows in 1 direction
  • from cells, batteries, DC generators
• plugs

  • brown wire ( live wire)
  • blue wire ( neutral wire)
  • yellow / green wire (earth wire)
• earth wire

  • provides a path of least resistance to earth
  • connects to the metal casing of appliances
  • if there is a fault, the live wire might touch the casing which means the casing would be live
  • there is a surge of current through the earth wire
  • this blows the fuse, isolating the device
• earthing

  • if charge gets the chance, it will flow to earth
  • sparks happen when a charge flows through an object it shouldn't go through or a person
• trampoline

  • as you bounce, charge builds up due to friction
  • when you are stood on the trampoline, charge doesnt flow to the ground because the material that the prampoline is made of is an insulator
  • when you touch the metal, charge flows to the ground through the metal legs (path of least resistance)
  • this causes you to recieve a small electric shock as current flows through you
• aircraft earthing cable

  • charge builds up on the plane because friction is created between the plane and the air when its in the sky
  • this means once the plane has landed the charge stays there because the tyres are made of rubber which is a good insulator
  • there is a problem because when the plane refuels, the charge will go through the pump becuase it is the path of least resistance
  • if the charge touches the fuel, it will explode
  • an earthing cable is added to the plane as a path of least resistance to the ground
  • when this happens, the plane can be discharged safely