In homes

• AC - Alternating current

  constant changing in direction

  Uk main supply = 230V , frequency of 50 (Hz)
• DC - direct current

  supplied by batteries

  flow one direction
• Cables - 3 wires

  live , neutral , earth

  covered by plastic insulation for safety
• Live wire - provides potential difference from mains

  colour - brown
• Neutral wire - completes cycle

  colour - blue
• Earth wire - protection

  stops appliances from becoming live

  carries current if there’s a fault

  colour - yellow and green
• Energy transferred - depends on how long appliances is on for and power
• Energy transferred ( J ) = Power ( W ) x Time ( s )

  E = Pt
• Energy transferred around a circuit when the charge moves

  Energy transferred ( J ) = charge flow ( C ) x potential difference ( V )

  E = QV
• Power ( W ) = Current ( A ) x Potential Difference ( V )

  P = VI
• 2 Power ( W ) = current2 ( A ) x resistance ( Ohm )

  P = I2R
• National Grid - system of cables and transformers

  transfer electrical power from the power station to where it’s needed

  power stations able to change the amount of electricity produced
• Step-up transformers = increase voltage as the electricity flows through the cables
• Step-down transformers - decrease the potential difference to make it safe