Conductors and insulators
When electricity flows through objects, it doesn’t always flow easily. Materials can be conductors or insulators, meaning they can let electricity flow through them easily or not.
Electrical conductors allow electric currents to flow through them easily. Conductors are used in wires that connect to electrical devices.
Silver, gold, aluminium, copper, iron, steel and water are all good conductors. Good conductors allow electric currents to move through them with little resistance. A conductor with high resistance would get very hot when the current flows through, this will waste a lot of electricity. Low resistance conductors save electricity.
The best conductors are metals. Silver is the best of all but it is rare and expensive, this is why it is not used in most electrical equipment. The most commonly used conductor is copper.
Insulators do not allow electric currents to flow through them easily. They are great at keeping us safe from electricity. The wire that carries electricity to our computers is covered with an insulator which stops electricity passing through it and electrocuting us.
Glass, air, rubber, wood, porcelain, plastic and paper are all good insulators.
Semiconductors are in between. They are very useful because their conductivity can be controlled allowing current to flow in just one direction or only sometimes. Silicon is a commonly used semiconductor.
Most good electrical conductors are also good heat conductors. Wood and plastic are often used for saucepan handles because they are good insulators (bad conductors), they stop the heat passing through so we can touch the handles without getting burnt. The saucepan is made of metal because it is a good electrical and heat conductor. It lets heat pass from the cooker into the food.
- Resistance increases with temperature. Generally the higher the temperature the lower the conductivity.
- Heat does not pass through some materials like plastic, oven gloves, cork and wood. These materials are called thermal insulators.
- Natural insulators like bird feathers and animal fur often have pockets of trapped air to keep them warm.