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1.4Unit 9: Electricity and circuits

Conductors and insulators — Cambridge Checkpoint Physics 0893 Revision Notes & Topical Questions

5 min read 10 parts Lesson 4 of 5 1 quiz

📚 Cambridge Checkpoint Physics 0893 Hub / Topical Revision
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Lesson summary

1.4 Conductors and insulators — CHECKPOINT PHYSICS 0893 notes: Explain conductors and insulators in terms of free electrons and give their uses.Conductor = a material that conducts electricity and allows current to flow through itReason — in a conductor the electrons are free to …

  • Aluminium and steel
  • Printed circuits
  • Conductors and insulators together
  • Colour coding
  • Power lines
  • Safety and energy

Part 1 of 8Conductors

Conductor
Conductor a material that conducts electricity and allows current to flow through it
Reason
  • Reason in a conductor the electrons are free to move
Metals
  • Metals all metals are conductors
Wires
  • Wires wires that carry current are made from metals

Part 2 of 8Metals used for wires

Copper
  • Copper used in most wires in houses and schools, with a plastic coating
Aluminium and steel
  • Aluminium and steel used in long-distance wires because they are cheaper than copper
Printed circuits
  • Printed circuits phones and laptops use copper tracks instead of wires
Silver
  • Silver a better conductor than copper but too expensive for wires at home

Part 3 of 8Insulators

1Insulator
Insulator a material that does not allow current to flow through it
2Reason
  • Reason in an insulator the electrons are not free to move, so electron flow is inhibited
3Examples
  • Examples most non-metals, such as plastic, wood, air and cotton
4Conductors and insulators together
  • Conductors and insulators together steel and aluminium are conductors; plastic and wood are insulators

Part 4 of 8Uses of insulators

Plugs
  • Plugs the plastic body lets people touch the plug while the metal pins conduct
Wires
  • Wires plastic coatings protect people from electric shocks
Colour coding
  • Colour coding different coloured plastic identifies each wire
Power lines
  • Power lines insulators stop current flowing from the wires into the metal pylon
Safety and energy
  • Safety and energy otherwise energy would dissipate into the ground and people and animals would get shocks

Part 5 of 8Conductors compared with insulators

ConductorInsulator
ElectronsFree to moveNot free to move
CurrentFlowsDoes not flow
ExamplesMetals such as copper, aluminium, steelPlastic, wood, air, cotton
UseWires, plug pins, circuit tracksWire coating, plug bodies, pylon insulators

Part 6 of 8Testing materials

1
Build a circuit with a cell, a lamp, crocodile clips and wires.
2
Touch the crocodile clips together to check that the lamp lights, which shows the circuit works.
3
Connect each test material between the clips.
4
If the lamp lights, the material is a conductor.
5
If the lamp does not light, the material is an insulator.
6
Record the results in a table.

Part 7 of 8Metals that appear to be insulators

Reason
  • Reason a metal object may have a coating of paint, plastic or oxide that blocks the current
Check
  • Check rub the coating off or connect the clips to the bare metal to show it conducts

Part 8 of 8More from the specification

1Electrical conductors
  • Materials that contain mobile charge carriers (free electrons) and allow electric current to pass easily.
    • (such as copper, aluminium, and graphite)
2Electrical insulators
  • Materials whose electrons are tightly bound to atoms, preventing charge flow.
    • (such as plastics, rubber, glass, and ceramics)
3Safety insulation in appliances
  • Plastic sheathing and rubber coatings surround metal wires to prevent electric shocks and accidental short circuits.
4Testing material conductivity
  • Placing test samples in an open circuit gap;
    • lighting of the test bulb confirms the material is an electrical conductor.

Key terms

TermMeaning
ConductorMaterial that allows current to flow.
InsulatorMaterial that does not allow current to flow.
ConductAllow current to pass.
InhibitHold back or reduce.
Free electronsElectrons that can move through a material.
CopperMetal widely used for electrical wires.

Avoid these mistakes

1
Thinking all materials with metal on the outside conduct — a coating may insulate.
2
Thinking insulators have no electrons — their electrons are not free to move.
3
Thinking only copper is a conductor — all metals conduct.
4
Thinking air is a conductor — air is an insulator.

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