AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Most electrical appliances are connected to the mains using three- core…
Full specification wording
Mains electricity: Most electrical appliances are connected to the mains using three- core cable.
A three-core cable contains three separately insulated copper wires, live, neutral and earth, inside one flexible outer sheath.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 1 of 8
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A three-core cable contains three separately insulated copper wires, live, neutral and earth, inside one flexible outer sheath. 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.
What earns the marks
- Naming the three cores as live, neutral and earth.
- Copper as the conductor because it is a good electrical conductor.
- The plastic covering as an insulator that prevents contact with the conducting core.
- A double insulated appliance needing only two cores because its case is not metal.
Common mistakes and how to put them right
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.
Exam 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.
Try the lesson
The start of the Mains electricity: Most electrical appliances are connected to the mains using three- core cable. lesson, made from checked teaching notes for this specification point.
Have a go first
What type of cable is used to connect most electrical appliances to the mains supply?
Listen
A three-core cable contains three separately insulated copper wires, live, neutral and earth, inside one flexible outer sheath. 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. A strong answer earns marks for these points. naming the three cores as live, neutral and earth. copper as the conductor because it is a good electrical conductor. the plastic covering as an insulator that prevents contact with the conducting core. a double insulated appliance needing only two cores because its case is not metal. Exam tip: Use the exact names live, neutral and earth; 'positive' and 'negative' score nothing for an ac supply.
See it
Key words
Say what each word means before you turn the card.
three-core cable
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live neutral earth
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conductors and insulators
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double insulation
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See every definition
- three-core cable
- A cable containing three separately insulated copper wires, live, neutral and earth, inside one flexible outer sheath.
- live neutral earth
- The three cores of a mains cable; live and neutral carry the working current, and the earth core is a safety connection to the metal case.
- conductors and insulators
- The cores are copper because it is a good electrical conductor that bends without breaking, and each core is covered in plastic because plastic is an electrical insulator.
- double insulation
- An appliance with a plastic case, such as a hairdryer or a phone charger, uses a two-core cable because a plastic case cannot become live even if a wire works loose inside.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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