Power supplies GapFill

Domestic electrical appliances use mains electricity. This has an alternating potential difference with a value of  100 V50 V230 V120 V330 V80 V, at a frequency of  330 Hz100 Hz230 Hz120 Hz50 Hz80 Hz.
Mains electricity is delivered by three-core cables, which consist of the  grounddirectneutralearthlivestatic wire, which provides the potential difference, the  directearthgroundliveneutralstatic wire, which completes the circuit, and the  directliveearthgroundstaticneutral 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 = IR²P = R ÷ I²P = I² ÷ RP = R² ÷ IP = I ÷ R². The total energy transferred by a component is equal to  E = V ÷ QE = Q²VE = QV²E = Q ÷ VE = Q ÷ V²E = QV.
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 generatorsramping solenoidsstep-down transformerssliding solenoidsdrop-down generatorsstep-up transformers for transmission, and in homes the potential difference is decreased using  step-up transformersstep-down transformersboost-up generatorssliding solenoidsramping solenoidsdrop-down generators for use by appliances.