P5 Electricity in the Home - AQA Trilogy Physics

Alternating Current (a.c.)

Alternating Current (a.c.)

• mains electricity is an a.c. supply

• repeatedly reverses its direction - flows one way then the opposite way in successive cycles

• frequency is the number of cycles it passes through each sec

Direct Current (d.c.)

• flows in only one direction

Frequency of a.c. supply

• frequency = 1 / time taken for 1 cycle

Mains Circut

• every mains circuit has a live wire and a neutral wire

• live wire - alternating positive and negative every cycle

• neutral wire - remains at 0V

National Grid

• system of transformers and cables

• 50 Hz

• 230V

Three-Pin Plug

• stiff plastic case with double-insulating

• pins are made of brass as it is a good conductor that doesn’t rust or oxidise

• fuse between live pin and wire - if too much current passes through the wire in the fuse it melts and cuts the live wire off

Cables

• copper used as it is a good electrical conductor and bens easily

• plastic is a good electrical insulator

Power

• Power (W) = energy transferred to appliance (J) / time taken for energy to be transferred (s)

• P = E / t

• Power (W) = current² (A) x resistance (Ω)

• P = I² x R

• Power Supplied (W) = current (A) x pd (V)

• P = I x V