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Resistance and electrons
As the free electrons move through a solid they collide with the atoms of the material and this affects their motion causing resistance.

Some materials have more free electrons than others and so these materials have a low resistance.
A high resistance means that the free electrons will make lots of collisions and lose lots of energy.

You can compare this with a person struggling to get through a large crowd; they will also lose lots of energy as they collide with the people in the crowd.

© Keith Gibbs 2009