Mains electricity — AQA GCSE Physics
Test yourself on Mains electricity with AQA GCSE practice questions.
7 days Premium · Then free forever · No card, no charge
Mains electricity explained
A three-core cable contains three separately insulated copper wires, live, neutral and earth, inside one flexible outer sheath.
Read the full explanation
The cores are copper because it is a good electrical conductor that bends without breaking; each core is covered in plastic because plastic is an electrical insulator, and the outer sheath adds a second insulating layer and holds the three cores together. Live and neutral carry the working current, and the earth core is a safety connection to the metal case. Not every appliance needs all three: an appliance with a plastic case, such as a hairdryer or a phone charger, is double insulated and uses a two-core cable, because a plastic case cannot become live even if a wire works loose inside.
Your focus
- Name the three cores of a mains cable and state the job of each one.
- Explain the choice of copper for the cores and plastic for the covering using the words conductor and insulator.
- Justify why a plastic-cased appliance can be supplied safely by a two-core cable.
Mains electricity exam tips
Marking Points
- one mark for naming the three cores as live, neutral and earth
- one mark for copper as the conductor because it is a good electrical conductor
- one mark for the plastic covering as an insulator that prevents contact with the conducting core
- one mark for a double insulated appliance needing only two cores because its case is not metal
Examiner Tips
- 💡Use the exact names live, neutral and earth; 'positive' and 'negative' score nothing for an ac supply.
- 💡If the appliance in the question has a plastic case, expect a two-core answer and say why.
- 💡Link each material to a property: copper conducts, plastic insulates.
Common Mistakes
- naming the third core as the 'ground wire' or the 'positive wire' rather than the earth wire
- saying the cable has three cores because the appliance needs three separate currents
- claiming every appliance must be earthed, ignoring double insulated plastic-cased devices
- describing the plastic sheath as a conductor that carries stray charge away