Energy

• Renewable energy is energy sources that are constantly being replenished as they are used.

  Eg.

  • Solar power
  • Hydroelectric power
  • Tidal power
  • Wind power
  • Biofuels (although they still release CO2)
  • Geothermal power
• Non-renewable energy is energy sources that are being used faster than they are being replaced.

  Eg.

  • Oil power station
  • Coal power station
  • Natural gas power station
  • Nuclear power
• Nuclear power

  Pros:

  • Lots of energy released
  • Fuel is readily available
  • No greenhouse gases produced

  Cons:

  • Expensive + difficult to store waste
  • Slow start-up time
  • High risk of large-scale accident
• National grid

  Power station (25,000W) --> Step-up transformer (400,000W) --> Step-down transformer --> Consumers (230W) --> Live wire (brown) --> Appliance --> Earth wire (green + yellow)
• Power loss in transmission lines is proportional to current².

  Therefore if current increases 4x, power loss increases 2x.
• In the UK, electricity is:

  • 230V
  • 50Hz
• UK plug

  Live wire (Brown wire)

  • Carries current into appliance
  • Always attached to a fuse

  Neutral wire (Blue wire)

  • 0V
  • Makes the circuit complete

  Earth wire (Green and Yellow stripy wire)

  • Safety wire
  • Prevent appliance becoming live

  
• The fuse connected to the live wire will melt if the current is exceeded.

  Eg. A 5A fuse melts >5A, breaking the circuit and stopping the current

  The thickness of the wire surrounding the fuse determines how much current can flow through it before it melts.
• An isolating transformer is a safety device with the same number of coils on primary and secondary, and allows you to use an electrical device without being directly connected to the mains.
• Circuit breaker = Can 'trip' and break a circuit when the current gets to high, but are easily reset. (similar to a fuse)
• In a transformer, an alternating magnetic field is induced in the iron core.
• Transmitting energies at high voltages in transformers reduces the energy that is lost as heat due to the resistance of the cables.
• The higher the current in a transformer, the more power is lost