supplying electricity

• What type of current is provided by a cell?

  Direct current (d.c.)
• What does 'a.c.' stand for in the context of electrical current?

  Alternating current
• What kind of current is supplied by mains electricity?

  Alternating current (a.c.)
• What is the typical frequency of mains electricity in the UK?

  50 Hz
• What is the typical voltage of mains electricity in the UK?

  230 V
• What color is the live wire in a three-core cable?

  Brown
• What color is the neutral wire in a three-core cable?

  Blue
• What color is the earth wire in a three-core cable?

  Green and yellow
• What is the primary function of the live wire in a three-core cable?

  Carries the alternating current
• What is the function of the neutral wire in a three-core cable?

  
  

  complets current
• What is the main function of the earth wire in a three-core cable?

  Connects to the earth for safety
• Under what condition does current flow in the earth wire?

  When there is a fault
• Why is the live wire dangerous?

  It carries a high voltage
• What is the National Grid?

  Electricity transmission network
• What is the purpose of step-up transformers in the National Grid?

  Increase voltage for efficient transmission
• What is the purpose of step-down transformers in the National Grid?

  Decrease voltage for home use
• How does a large potential difference in transmission cables help energy transfer in the National Grid?

  It reduces current and energy loss
• Why is the National Grid an efficient way to transfer electricity?

  Less energy is wasted
• What two factors does energy transfer to an appliance depend on?

  Power and time
• What is the unit for power?

  Watt (W)
• What is the unit for current?

  Ampere (A)
• What is the unit for potential difference?

  Volt (V)
• What is the unit for resistance?

  Ohm (Ω)
• In which direction does direct current (d.c.) flow?

  Only in one direction
• What best describes alternating current?

  Repeatedly reverses direction
• What is the relationship between current and resistance?

  Current decreases with increased resistance
• What is the function of supplying electricity?

  Supplying electricity
• What is the characteristic of current flow in supplying electricity?

  Flows only in one direction
• What type of current repeatedly reverses direction?

  Alternating current
• What is the frequency and voltage of alternating current?

  50 Hz, 230V
• What colour is the live wire?

  Brown
• What colour is the neutral wire?

  Blue
• What colours are the earth wires?

  Green and yellow
• What does the cable do?

  Carries the alternating potential difference from supply
• What does the neutral wire do?

  Completes the circuit
• What is the earth wire's function?

  Safety wire, stops appliance becoming live
• What does the earth wire provide?

  Large p.d. causing large current through person
• What links power stations to customers?

  Nationwide network of cables and transformers
• What do transformers do to potential difference from power station to transmission cables?

  Increase the p.d.
• What do transformers do to potential difference from transmission cables to mains supply?

  Decrease the p.d.