Miniature Circuit Breakers (MCB)


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Miniature Circuit Breakers (MCB)

  • Replace fuses
  • designed to switch off the current if too much electricity flows.
  • prevents overheating,and perhaps a fire.
  • Contain an electromagnet.
  • Current is higher than the rated value, the strength of the electromagnetic is enough to seperate the electrical contacts inside, this switches the circuit off.


  • Can be reset - no need to be replaced.
  • Switches off faster than fuses.


  • They do not protect you if you touch a live wire.
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Residual Current Devices (RCD'S)

  • Does the same as Earth wires.
  • Turns current off when there is a diffrence between the live and neutral wires (prevents user from having an electric shock).
  • When live and neutral currents different electromagnetic seperates contact which stops current.
  • Designed to stop you getting an electric shock.
  • Should be used with power tools and any electrical device outdoors.
  • Current in the live and neutral wires should be equal.
  • Touch a live wire by accident and some current will flow through you to the Earth - the there will be a diffrence in the current in the neutral and live wires.
  • Detects the diffrence in current and immeadiatley throws the switch to break the circuit.
  • Circuit is again broken by an electromagnet
  • Advantages - Detects a very small diffrence in current,Switches of very quickly.Disadvantages - Get a shock, but because the RCD switches off very quickly, the shock will not kill you.

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