8.9 - Fuses & Earthing

• What is a common problem when dealing with electricity?

  Sudden increases in current, called surges
• What can cause surges in electrical circuits?

  Changes in a circuit or faults in appliances
• What are the potential dangers of electrical surges?

  They can cause fires or electric shocks
• What safety precautions help reduce electrical risks?

  • Fuses
  • Circuit breakers
  • Earth wires
  • Double insulation
• How do fuses and circuit breakers function similarly?

  Both break the circuit during high current
• What is a fuse made of?

  A very thin piece of wire
• What happens to a fuse during a surge?

  The thin wire melts, breaking the circuit
• How are fuses typically packaged?

  In little cases with thin wire inside
• What rating fuse should you use for a 3 amp appliance?

  A 5 amp fuse
• One risk in electric circuits is a surge in current. The sudden increase in current can damage the appliance, cause a fire, or give an electric shock.
• Why should a fuse rating be above the appliance's current?

  To prevent breaking during normal operation
• What is a disadvantage of fuses?

  They are permanently broken after a surge
• How do circuit breakers differ from fuses?

  Circuit breakers can be reset after tripping
• What is a downside of circuit breakers?

  They are more expensive than fuses
• How can surges cause harm through loose live wires?

  They can touch the casing, causing shocks
• What is the purpose of earthing in electrical appliances?

  To provide an alternative pathway for current
• How does double insulation prevent electric shocks?

  It covers appliances in non-conductive plastic
• What type of wire is typically found in double insulated appliances?

  Live and neutral wires only
• What are the key features of fuses and circuit breakers?

  Fuses:

  • Simple and cheap
  • Permanently broken after a surge

  
  

  Circuit Breakers:

  • Can be reset
  • More expensive than fuses
• What is the main function of an earth wire?

  To divert current away from users
• What happens if an appliance has double insulation?

  It typically does not need an earth wire
• What is the purpose of the live wire in an appliance?

  To carry current to the appliance
• What is the role of the neutral wire in an appliance?

  To carry current away from the appliance
• Which of the following safety features are used to protect against surges in current?

  • Circuit breakers
  • Fuses
• Fuses 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.
• Circuit breakers are like a ________ that can be reset after they break the circuit.

  fuse
• How earth wires protect us from electric shocks:

  • The earth wire is connected to the casing of the appliance.
  • If the live wire touches the appliance casing, the earth wire provides an alternative pathway for electricity to flow.
  • This way, we don't get an electric shock from touching the live appliance casing.
• An appliance has 'double insulation'. Therefore it most likely:

  • Has a plastic casing, but no earth wire
  • This may seem counter-intuitive because 'double' insulation makes it seem like it has both a casing and earth wire, but remember that 'double insulation' usually refers to just having a plastic casing.