P4 - Safe electricals

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  • Created by: Naomi
  • Created on: 21-01-13 17:25
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  • Safe electricals
    • Resistance
      • A measure of how hard it is for current to flow
      • Factors that may affect resistance are:
        • Length (of wires)
        • Material
        • Thickness (cross section area)
        • Temperature
      • Measured in Ohms
    • The live wire carries a high voltage around the house
      • It is the brown wire
    • The neutral wire completes the circuit, providing a return path for the current
      • It is the blue wire
    • The earth wire is connected to the case of the appliance to prevent it becoming live
      • It is the green and yellow wire
    • The fuse contains wire which melts if the current becomes too large
      • No current can flow, preventing overheating and furthur damage to the appliance
      • Earth wires and fuses stop a person receiving an electric shock if they touch a faulty appliance
        • The earth wire is connected to the case of the appliance to prevent it becoming live
          • It is the green and yellow wire
        • As soon as the case becomes 'live', a large current flows in the earth wire and the fuse blows
      • A resettable fuse (circuit breaker) doesn't need to be replaced to restore power, it can be reset
    • Current
      • The flow of electrons
        • Measured in amps
    • Voltage/potential difference
      • A measure of energy carried by an electric current
        • Measured in volts
    • Electrical power
      • The rate at which an appliance transfers energy is its power rating
        • power = voltage x time
          • The formula for electrical power can be used to calculate the correct fuse to use in an electrical device

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