Electricity

Lightning is the most visible way we see electricity in nature

Electricity is a type of energy found in nature. We see it in nature when we see a lightning flash or when we stroke an animal and feel sparks.

Scientists have also found we can make electricity if we pass a magnet close to a metal wire or if we put the right chemicals in a jar with two different kinds of metal rod.

Scientists have observed that electricity seems to flow like water from one place to another, either as a spark or as a current in a metal. They now know that all matter has electric charge but this is mostly canceled out by the presence of matter with an opposite charge. We only see an effect when there is too much or too little electric charge in one place so that it is not canceled out.

Since the nineteenth century electricity has been made into a useful thing that affects every part of our lives. Until then it was just a curiosity or a force of nature seen in a thunderstorm.

To be useful electricity has to be made from other sources of energy such as by burning coal or oil or from wind or flowing water in a power station.

Electricity arrives at our homes through wires from the places where it is made. It is used by Electric Lamps for producing light, Electric Heaters to produce heat etc. It is also used by many devices like washing machines, Electric Cookers, etc for doing work. In factories, electricity is used for running machines and computers.

The people who deal with electricity and electrical devices in our homes and factories are called "Electricians".

Electricity in physics

Electricity works because electric charges push and pull on each other. There are two types of electric charge, positive charge and negative charge. Two positive charges repel each other. This means that if you put two positive charges close together and let them go, they would fly apart. Two negative charges also repel. But a negative charge and a positive charge attract each other. This means that if you put a positive charge and a negative charge close together, they would smack together. A short way to remember this is the phrase opposites attract, likes repel.

Electric charges can push or pull on each other even though they are not touching. This is possible because each charge makes an electric field around itself. An electric field is an area that surrounds a charge. At each point near a charge, the electric field points in a certain direction. If a positive charge is put at that point, it will be pushed in that direction. If a negative charge is put at that point, it will be pushed in the exact opposite direction.

All the matter in the world is made of tiny positive and negative charges. The positive charges are called protons, and the negative charges are called electrons. Protons are much bigger and heavier than electrons, but they both have the same amount of electric charge, except that protons are positive and electrons are negative. Because "opposites attract," protons and electrons stick together. A few protons and electrons can form bigger particles called atoms and molecules. Atoms and molecules are still very tiny. It is impossible to see them without a very powerful microscope. Any big object, like your body, has more atoms and molecules in it than anyone could count.

Because negative electrons and positive protons stick together to make big objects, all big objects that we can see and feel are electrically neutral. Electrically is a word meaning "describing electricity" and neutral is a word meaning, "balanced." That is why we do not feel objects pushing and pulling on us from a distance, like they would if everything was electrically charged. All big objects are electrically neutral because there is exactly the same amount of positive and negative charge in the world. We could say that the world is exactly balanced, or neutral. This seems very surprising and lucky. Scientists still do not know why this is so, even though they have been studying electricity for a long time.

Electric current

A drawing of an electric circuit. The current (I) flows from + round the circuit back to -
Electricity is sent on wires.

In some materials, electrons are stuck tightly in place, while in other materials, electrons can move all around the material. Protons never move around a solid object because they are so heavy, at least compared to the electrons. A material that lets electrons move around is called a conductor. A material that keeps each electron tightly in place is called an insulator. Examples of conductors are copper, aluminum, silver, and gold. Examples of insulators are rubber, plastic, and wood. Copper is used very often as a conductor because it is a very good conductor and there is so much of it in the world. But sometimes other materials are used.

Inside a conductor, electrons bounce around, but they do not keep going in one direction for long. But if an electric field is set up inside the conductor, the electrons will all start to move in the direction opposite to the direction the field is pointing (because electrons are negatively charged). A battery can make an electric field inside a conductor. If both ends of a piece of wire are connected to the two ends of a battery (called the electrodes) the loop that was made is called a circuit. Electrons will flow around and around the circuit as long as the battery is making an electric field inside the wire. This flow of electrons around the circuit is called electric current.

A conducting wire used to carry electric current is often wrapped in an insulator like rubber. This is because wires that carry current are very dangerous. If a person or an animal touched a bare wire carrying current, they could get hurt or even die depending on how strong the current was. You should be careful around electrical sockets and bare wires that might be carrying current.

It is possible to connect an electrical device to a circuit so that electrical current will flow through a device. This current will make the device do something that we want it to do. Electrical devices can be very simple. For example, in a light bulb, current flows through a special wire called a filament, which makes it glow. Electrical devices can also be very complicated. Electricity can be used to drive a motor inside a tool like a drill or a pencil sharpener. Electricity is also used to power modern electronic devices, including telephones, computers, and televisions.

Some terms related to electricity

Methods of generating electricity

Electricity is made in power stations

Electricity is mostly generated in places called power stations. Power stations use heat to turn water into steam. The force of the steam pressure turns giant fan-like structures called turbines, which are linked to machines called 'generators'. Generators pass wires through strong magnetic fields to generate electricity.

Sometimes a natural flow such as wind or water can be used to directly turn a generator so no heat is needed.

There are many sources of heat which can be used to generate electricity. Heat sources can be classified into two types: renewable energy resources in which the supply of heat energy never runs out and non-renewable energy resources in which the supply will be eventually used up.

Renewable energy resources

Renewable heat energy
  • Solar thermal power
  • Geothermal power
Renewable flow energy
  • Hydro-electric power
  • Wind power
  • Wave power
  • Tidal power

Non-renewable energy resources These all use heat as a source of energy.