Section 1 of 4Conductors
A conductor lets charge flow through it easily, and in metals the charge carried is by electrons.
Conductor
- A material that allows charge, usually electrons, to flow through it easily.
Metal structure
- A metal consists of positive metal ions in a lattice, with their outermost electrons delocalised and free to move.
Examples
- Silver, copper, aluminium and steel are good conductors because they contain many electrons that are free to move.
Link to current
- Current is the rate of flow of charge, so the more easily electrons flow, the better the material conducts.
Section 2 of 4Insulators
Insulators
Definition
- An insulator has no free charges, so it does not allow charge to flow through it easily.
Examples
- Rubber, plastic, glass and wood are common insulators used to cover or support electrical equipment.
Limited conduction
- Some non-metals such as wood conduct a little, mainly in the form of static electricity on their surfaces.
Surface charge
- Two insulators that touch can allow charge on their surfaces to be conducted away between them.
Section 3 of 4Conduction in Practice
1
In a copper wire, the outer electrons of each copper atom are free to drift when a potential difference is applied.
2
The drifting electrons carry charge along the wire, which is what we measure as current.
3
In an insulator such as rubber, the electrons are held tightly in their atoms, so almost no charge can move through it.
4
Metals therefore make good wires for connecting components, while plastic or rubber is used as the covering around them.
Section 4 of 4Exam Checklist & Tips
2.4.1 – Key Points for the Exam
- Conductor A material that allows charge to flow through it easily, such as a metal.
- Insulator A material that does not allow charge to flow through it easily because it has no free charges.
- Delocalised electron An outer electron in a metal that is free to move through the lattice of ions.
- Lattice A regular arrangement of ions, as found in a metal conductor.
- Free charge A charge that is able to move through a material, such as an electron in a metal.
Common Mistakes
- Saying metals conduct only because they contain electrons;
- it is the delocalised electrons that are free to move.
- Stating that insulators contain no electrons at all;
- electrons are present but are held tightly in their atoms.
- Describing the moving charges in a metal as positive; in metals the moving charges are electrons.
- Claiming that current flows through insulators easily; insulators allow almost no current to flow.