P1- 1.4

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P1- 1.4- CONDUCTION

It is important to know which materials are good CONDUCTORS and which are good INSULATORS

-Metals are better conductors than non-metals

-Copper is a better conductor than steel

-Wood conducts better than glass

Conduction in metals:

-Metals contain lots of FREE ELECTRONS

-These electrons move about at random inside the metal and hold the positive metal ions together

-They collide with each other and with the positive ions (Ions are charged particles)

When a metal rod is heated at one end:

-The free electrons at the hot end gain kinetic energy and move faster

-These electrons DIFFUSE and collide with other free electrons and ions in the cooler parts of the metal

-They transfer kinetic energy to these electrons and ions

THE ENERGY IS TRANSFERRED FROM THE HOT END OF THE ROD TO THE COOLER END

In non-metallic solids, all the electrons are held in the atoms. Energy transfers take place when they vibrate. This is less effective than energy transfer by free electrons.

METALS ARE BETTER CONDUCTORS THAN NON-METALS