Domestic electricity

• difference between a.c and d.c

  . alternating current continuously changes direction and magnitude

  . direct current has a constant direction
• UKs main supply in V and Hz

  230V

  50hZ
• what is a fuse

  breaks the circuit when the current exceeds a set value
• mcb


  miniature circuit breaker

  . easily reset

  . protects the circuit
• rccb


  residual current circuit breaker

  . switches off current when there is a difference between current in live and neutral wires.

  .More sensitive than mcb

  .protects user
• what is a ring main


  a looped parallel circuit
• advantages of a ring main

  . cables can be made thinner because there are two paths of each current

  . each part of cable carries less current because current flows 2 ways

  . more convenient since sockets can be placed anywhere on ring main
• function of live wire

  brown wire that carries current to the house/appliance at a high voltage
• function of neutral wire

  brown wire that completes circuit and carries current away at low voltage
• function of earth wire


  green and yellow wire that is a safety wire that carries current safely into the ground if a fault develops in a metal framed appliance.
• where are switches and fuses placed

  switches and fuses are placed into live wire
• what happens when a metal framed appliance becomes live

  a large current can flow along earth wire and this high current will blow a fuse or trip a mcb.