electricity in the home

• What are the differences between AC and DC supplies?

  • Mains supply = AC
  • Battery supply = DC
  • AC: voltage alternates
  • DC: voltage is constant
• What type of current does the UK mains supply use?

  Alternating current
• What is the frequency and voltage of the UK mains supply?

  50 Hz and 230 V
• What color is the live wire in a circuit?

  Brown
• What is the function of the neutral wire?

  Completes the circuit at 0 V
• What is the purpose of the earth wire?

  For safety, carries current away
• How do earthing and fuses prevent electrical overloads?

  • Surges in current can cause damage
  • Earth wire carries current away if fault occurs
  • Fuses melt to break the circuit during overload
• How are fuses connected in a circuit?

  Connected to the live wire
• What should the rating of a fuse be?

  Just higher than normal operating current
• What is the voltage of the live wire?

  230 V
• What is the voltage of the neutral and earth wires?

  0 V
• What happens if you touch a live wire?

  Causes electric shock
• Why is there still a danger of electric shock when a switch is off?

  Potential difference remains in live wire
• What can happen if there is a connection between live and neutral wires?

  A huge current can flow, causing fire
• What is AC supply

  alternating current

  • current reverses direction every half cycle
  • current oscillates at a frequency of 50Hz in the UK
• Which wire should fuse be connected to?

  Live
• Why do metal appliances need to be earthed?

  If the live wire touches the casing it might become live. Earthing the case prevents the user getting an electric shock in the event of a fault

  All current would flow to the ground instead of through the user
• Role of earth wire

  Earth wire is connected to the metal case keeping the case at 0 V. This prevents the user from getting an electric shock
• Role of cable grip

  holds the cable in place to prevent wires from becoming loose
• Why is live wire and neutral wire connection dangerous?

  • if the link creates a low resistance path to earth, a huge current will flow
  • could result in fire
• What does the body provide?

  • provides a link between supply and earth
  • so current flows causing electric shock
• Why are switches connected in live wire?

  • so circuit can be broken
  • appliance becomes isolated
  • and risk of electric shock reduced
• Potential difference between live wire and neutral wire = ?

  supply potential difference, 230V