Fuses & Earthing

• What is a surge?

  A sudden increase in current
• Name 3 examples of what can cause a surge to occur.

  A fault in the circuit or appliance

  When you turn the appliance on/off

  Damaging an appliance
• Why are surges so dangerous?

  Surges can cause fires and electrical shocks
• What is a fuse?

  A very thin piece of wire connected to the live wire and prevents surges
• What are the advantages of a Fuse?

  Simple and cheap
• What are the disadvantages of a Fuse?

  Single-use: permanently broken after a single surge

  Have to be replaced each time
• Name 4 safety precautions of surges

  Fuses

  Earth wire

  Double Insulation

  Circuit breakers
• What does a circuit breaker do?


  Breaks the circuit whenever theres a surge, they are tripped then turn off the circuit and can be reset
• What is an earth wire?

  A wire which provides an alternative pathway for the current to flow away - any electricity is diverted through the earth wire rather than us
• What is Double Insulation?

  Extra insulation to prevent electric shock. For example, an entire appliance is covered in a plastic casing
• Name some advantages of Double Insulation

  No exposed metal parts

  plastic doesnt conduct electricity which means you cant get an electric shock from touching it

  Earth wires would not be required - only live and neutral
• Name a disadvantage of circuit breakers

  They are more expensive than fuses
• Name the complex process of how a surge it stopped through a fuse

  Surge —> heats up wire of the fuse —> melts —> breaks the circuit —> no more current can flow through it
• Name one risk in electrical circuits

  Surges - a sudden increase in voltage can damage the appliance, cause a fire, or cause an electric shock
• Which following safety features are used to protect against surges in currents?

  Circuit Breakers and Fuses
• Describe how fuses work

  They have a thin wire which melts and breaks the circuit when the current is too high

  The rating of a fuse is the current that will cause the fuse to break the circuit
• What fuse rating would be appropriate for a kettle that is designed to operate at 5A of current?

  8A
• Circuit breaks are like a…

  Fuse that can be reset after they break the circuit
• How do earth wires protect us from electric shocks?

  1. The earth wire is connected to the casing of the appliance
  2. If the live wire touches the appliance casing, the earth wire provides an alternative pathway for electricity to flow through
  3. this way, we dont get an electric shock from touching the live appliance rating