In order to understand how a home electrical installation works, one need to understand the basics of electricity itself. In this article I will try to explain in an easy to understand way how electricity is produced, and how it is utilized by the simplest equipment, the light bulb, to produce light. This article is not for technicians or engineers. It is for those people who have been using electricity all their lives without knowing at all how it works, how it causes fire or how it kills people.
a) How is Electricity Produced?
The discovery of electricity is one of the most important discoveries of our world. It is from electricity that many of the wonderful modern inventions have been created. The refrigerator, the electric bulb, radio and telephone have all been invented after the discovery of electricity.
Two things have allowed the production of useful electricity: magnetic field and electrons. Magnetic field is an invisible force and it has always been around us. The earth itself produces magnetic field. That is why we can use a compass to tell a direction correctly and consistently. The needle of a compass always align itself with the earth's magnetic field. In other words, the earth magnetic field forces the compass needle to align itself. This means the magnetic field can exert an invisible force on some things.
The second is something that scientists call electrons. Actually electrons are present in all matters. But it is the electrons within metal materials that were found useful for the production of electricity. The electrons within a length of metal can easily travel along the length of the metal when it is moved within a magnetic field. The magnetic field used to produce electricity is not the earth's magnetic field, but from magnets. When it was first discovered magnets were just natural materials found in the environment, but later development of knowledge and technologies allow it to be artificially produced.
Electricity that we use in our homes comes from power plants. In order to produce electricity, metals in the form of wires are continuously moved at high speed within a strong magnetic field. The energy to keep moving the wires within the magnetic field comes from coals, nuclear fuels or even the wind energy. The continuous movement creates a continuous flow of electrons along the metal wires.This electron flow is what we call electric current.
By having cables (i.e. metal wires insulated by materials that cannot conduct electrons) connecting the power plant to our houses, the flow of electrons is channeled to our homes. Of course we can buy our own power plant if we want, that is the small electric power generator. In that case we can actually disconnet the cables from the power company and connect the small electric generator with cables directly to the house distribution board. I will post some articles on these small electric generators later, but for now let's just concentrate on the basics of electricity first.
b) How Does a Bulb Produce Light
At the power plant, coal or other sources of energy is used to power machines that force huge numbers of electrons to continuously flow along the inside electrical wires and cables into our houses. When inside a house, the electrons continue flowing along the inside the house wiring cables into the electric bulbs and other electrical appiances.
The light bulb itself has two insulated cables connected to it. One is the live cable, and the other is the neutral or "return" cable. The electrons flow from the power plant to the light bulb inside the house through the live cable and flow back to the power plant through the neutral cable. That is why it is also called the "return" cable.
What if the return wire is broken, and the electrons cannot flow back to the power plant? Then the electrons cannot flow (i.e. no current flow) and the light bulb will not light up. This is to say that the the electrons must keep flowing continuously from the power plant to the house and back to the power plant, and then back again to the the house, again and again. In other words they move back and forth in circle, or in a "loop".
This is one of the most important requirements of an electrical installation for it to work properly and safely: the electrons must be able to keep flowing inside the live and the neutral cables in a "loop".
If the loop is broken (i.e. the wire or the cable is broken somewhere along its path), then what will happen to the electricity? The electrons inside the live cable just before the wire break are still there, and they are still under the force of the the magnetic field at the power plant. If a person accidentally touch the metal wire or the metal part of the insulated cable, that person will get electrocuted. This is because the electrons are still under force or under pressure, just like the the water under pressure in a water pipe. When come into contact, the electrons inside the wire will try to flow through the human body to go into the earth mass. They will try to do this in order to flow back to the power plant to complete the "loop".
As explained above, when the loop is broken the bulb will not light up, but the electron under pressure are still there unless the power plant is shut down. This is one of the common scenarios very dangerous to home users. But it is a topic suitable for a separate article by itself.
So how does the light get produced inside a bulb? Inside the bulb is a length of a very thin metal wire that lets the electrons flow through. However this wire is very thin, and when huge quantities of electrons flow through it continuously, the electrons keep knocking on each other while flowing through at the thin section. This electron behaviour releases a lot of heat energy, making the wire so hot that it glows, releasing heat and light. That is how we get the light from the bulb.
That's it for now. In future articles we will continue our journey along the flow path of the electrons so we can better understand their behaviour. This is very important in order to understand how the home electrical installation works and how to ensure the safety of our families and properties.