Power supplies GapFill

Domestic electrical appliances use mains electricity. This has an alternating potential difference with a value of  120 V100 V230 V50 V, at a frequency of  50 Hz230 Hz100 Hz120 Hz.
Mains electricity is delivered by three-core cables, which consist of the  neutraldirectstaticlive wire, which provides the potential difference, the  staticlivedirectneutral wire, which completes the circuit, and the  staticdirectearthlive wire, which is for safety purposes and only carries a current if there is a fault in the appliance.
Circuits transfer power at a rate equal to P = VI, or  P = I²RP = R ÷ I²P = IR²P = I ÷ R². The total energy transferred by a component is equal to  E = Q ÷ V²E = QVE = QV²E = Q ÷ V.
Mains electricity is delivered by the National Grid, which connects power stations to homes and businesses. At power stations, the potential difference of the electricity is increased using  boost-up generatorsstep-up transformersdrop-down generatorsstep-down transformers for transmission, and in homes the potential difference is decreased using  drop-down generatorsboost-up generatorsstep-up transformersstep-down transformers for use by appliances.