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Copper in health
 Properties 
Copper's properties
Copper has many useful properties. For example, it is:
(click on these to find out more)

Metal Conductivity
copper 640
silver 670
aluminium 410
mild steel 70
Table 1. Electrical conductivity. The values are a measure of how much current will flow in a standard sample when it is attached to 1 volt.

These have led to its use in a number of applications throughout history. Now, its most important property is it electrical conductivity.

Electrical conductivity
Copper has the best electrical conductivity of any metal, except silver. A good electrical conductivity is the same as a small electrical resistance.

Interactive photo of church steeple and lightning conductor
Picture 1 A lightning conductor carries the charge safely to ground.
Applications
Copper wires allow electric current to flow without much loss of energy. This is why copper wires are used in mains cables in houses and underground (although overhead cables tend be aluminium because it is less dense). However, where size rather than weight is important, copper is the best choice. Thick copper strip is used for lightning conductors on tall buildings like church spires. The cable has to be thick so that it can carry a large current without melting.

Copper wire can be wound into a coil. The coil will produce a magnetic field and, being made of copper, won't waste much electrical energy. Copper coils can be found in:

Device Uses
Electromagnets locks, scrapyard cranes, electric bells. (see electromagnets)
Motors pumps, domestic appliances (washing machines, dishwashers, fridges, vacuum cleaners), cars (starter motors, windscreen wipers, electric windows), computers (disc drives, fans), entertainment systems (walkman, video player, CD and DVD players). (see electric motors)
Dynamos bicycles, power stations.
Transformers mains adaptors, electricity substations, power stations.

You can find out more about the electrical uses of copper in:

Interactive graphic of ions and electrons
Picture 2. A copper wire is made of a lattice of copper ions. There are free electrons that move through this lattice like a gas.
How copper conducts
Copper is a metal. It is made up of copper atoms closely packed together.

If we could look closely enough, we would see that there are electrons moving about between the copper atoms. Each copper atom has lost one electron and become a positive ion. So copper is a lattice of positve copper ions with free electrons moving between them. (The electrons are a bit like the particles of a gas that is free to move within the edges of the wire).

The electrons can move freely through the metal. For this reason, they are known as free electrons. They are also known as conduction electrons, because they help copper to be a good conductor of heat and electricity.

The copper ions are vibrating. Notice that they vibrate around the same place whereas the electrons can move through the lattice. This is very important when we connect the wire to a battery.

Interactive graphic of electrical conduction
Interactive graphic of electrical conduction
Picture 3. When an electric current flows in a wire, the electrons move through the wire.
Conducting electricity
We can connect a copper wire to a battery (picture 3) and a switch. Normally, the free electrons move about randomly in the metal.

When we close the switch, an electric current flows. Now the free electrons flow through the wire (in picture 3, they are moving from left to right - although they still move randomly as well).

Electrons have a negative charge. They are attracted to the positive end of the battery. The free electrons move through the copper, flowing from the negative to positive terminal of the battery (note that they flow in the opposite direction to conventional current; this is because they have a negative charge).

The copper ions in the wire vibrate. Sometimes an ion blocks the path of a moving electron. The electron collides with the ion and bounces off it. This slows down the electron. Some of its energy has been transferred to the ion, which vibrates faster.

In this way, energy is transferred from the moving electrons to the copper ions. The copper gets hotter. This explains why:

  • metals have electrical resistance;
  • metals get hot when a current flows through them.

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Question 3
Most metals are conductors of electricity. However, apart from , copper is the best. Most cables are made of copper because it is . Metals conduct well because they have free . These are attracted to the terminal of a battery and move easily through the lattice of metal ions.