Conductors and Insulators
Based on the resistance they offer to the flow of current, materials are said to be Conductors or Insulators.
Conductors
A conductor is an object or material that allows the flow of electrical current with low resistance. Since the ability of a material to conduct electrical current depends on the number of free electrons, conductors are materials that have an abundance of free electrons. Metals are the best electrical conductors.
For the current to flow, one electron does not need to travel all the way from the source to the destination. The electron only needs to push a neighbouring electron, which in turn will push its neighbour and so on, until the final electron is pushed to the destination, completing the current flow. This makes metals an ideal choice for a conductor since metals characteristically have electrons wih enough mobility to be pushed along.
Examples of good conductors are metals such as copper, aluminium, and silver and non-metals such as carbon. While metals are very good conductors of electricity, they will still offer some resistance to the flow of electrons. This resistance to the flow of an electrical current gets converted to heat which is why conductors become hot. The resistance increases as the temperature increases.
Insulators
Insulators are materials that inhibit the flow of electrical current. They are the opposite of conductors. Their atoms have tightly bound electrons that cannot move easily throug the material. Materials like plastic, rubber, and wood are good insulators.
In any electrical system, insulators play a very important role. It is important that electricity flows through a conductor along a specific path. Conductors (such as wires in an electrical circuit) cannot randomly connect with each other, they must only connect as designed to enaure the flow of current is along the required path. To ensure this, insulators are placed between conductors to prevent the random flow of electricity.
The most common use of insulators, with plastic, cloth, or rubber as the material of choice, is around the electrical wires that supply electricity to and around your home. Each set of wires follows a specific path to drive a particular load (such as your lights and appliances). But there are many points, especially where they meet at the area for switches, where the wires may touch each other. Without insulation, the current would have flown randomly across the wires, making the set of circuits useless and dangerous.
Current can flow through the human body. The earth can be considered to be a point of very low voltage (a reference zero voltage). If you touch a metal wire carrying a current, your body will act as the medium through which the current would flow, the return point being the earth. This action could be dangerous if the current is very high, hence all conductors carrying electricity are covered with insulators.
