Physics · Electricity. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
A cell gives a direct potential difference: it always pushes charge the same way. Mains electricity is alternating: the p.d. keeps changing direction. UK mains is ac with a frequency of 50 Hz and a p.d. of about 230 V.
Most appliances use a three-core cable. The live wire carries the alternating p.d. from the supply. The neutral wire completes the circuit. The earth wire is a safety wire and carries current only if there is a fault.
The National Grid is the system of cables and transformers that links power stations to consumers. It transmits electricity at a very high p.d. so that the current is small and less energy is wasted heating the cables.
In E = Pt students leave the power in kW and the time in minutes. Change to watts and seconds first: 2.0 kW = 2000 W and 30 minutes = 1800 s.
Answer: Current = 5.0 A and energy = 138 000 J (138 kJ)
Type what you are stuck on. The helper finds the explanation, worked examples and the notes to read, free and instant.
← Series and parallel circuitsStatic electricity and electric fields →Take a Physics test