P2 - All About Electricity

Contains bulletpoint information on producing and distributing electricity, the dynamo effect, supplying electricity effectively, and electrical power.

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Producing and Distributing Electricity

  • National Grid - network of pylons and cables that covers the country
  • electricity taken from power stations to homes/industries
  • aim of power stations - convert a form of energy into electricty
  • a power station has 3 steps;
    • 1. generate steam
    • 2. pass steam through turbines, making them turn
    • 3. movement allows generator to turn it into electricity
  • power stations are innefficient, as energy is lost through sound and heat
  • fossil fuels: advantages - a concentrated source of energy. Disadvantages - causes acid rain and greenhouse gases, it's expensive to get from countries abroad, and it's unrenewable.
  • biomass: advantages - renewable, carbon neutral process, doesn't require imports of material. Disadvantages - takes time (and space) to grow, you need a lot of material to get enough energy.
  • nuclear power: advantages - quick, effective. Disadvantages - potentially dangerous.
  • photocells: advantages - renewable, sturdy, wireless, low maintenance. Disadvantages - doesn't work at night, energy reduced in bad weather.
  • wind power: advantages - cheap, renewable. Disadvantages - requires wind, looks ugly.
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The Dynamo Effect

  • electromagnetic induction; creating a voltage, and sometimes current, in a wire experiencing a change in magnetic field.
  • dynamo effect; using electromagnetic induction to turn kinetic energy into electricity.
  • electromagnetic induction happens when;
    • electrical conductor moves through magnetic field
    • OR magnetic field moves through electrical conductor
  • to reverse voltage or current, you need to reverse the direction of movement
  • increasing the strength of magnet, the number of turns on the coil or the speed of movement will make a bigger voltage and current
  • generators move coil in magnetic field, and every half turn the current swaps direction
  • generators produce AC
  • dynamos on bikes rotate magnet near coil
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Supplying Electricty Effectively

  • to transmit lots of electricity, high voltage/current in needed, but this means more heat energy wasted through cable.
  • cheaper to increase voltage while keeping current low, as less energy wasted through cable heat.
  • step-up transmformers increase voltage
  • step-down transformers make it safe to be used in homes
  • transformers only work on alternating current (AC)
  • power stations aren't efficient.
  • total energy input = useful energy output + waste energy output
  • efficiency = useful energy output / total energy input
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Electrical Power

  • power measured in watts (W) or kilowatts (kW)
  • 1 watt = 1 joule per second
  • to work out power of appliance: Power (W) = Voltage (V) x Current (A)
  • kilowatt-hour (kWh) is amount of energy converted by 1kW appliance
  • energy supplied (kWh) = power (kW) x time (h)
  • cost = number of units x price per unit
  • off-peak electricity is electricity supplied at night
  • advantages of off-peak electricity:
    • cost-effective for company
    • cheaper for consumers
  • disadvantages of off-peak electricity:
    • risk of fire in homes
    • stop enjoying use of electricity in day
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