Electricity is a form of energy that comes in positive and negative forms, that occur naturally (as in lightning), or is produced (as in generator). It is a form of energy which we use to power machines and electrical devices. When the charges are not moving, electricity is called static electricity. When the charges are moving they are an electric current, sometimes called 'dynamic electricity'. Lightning is the most known - and dangerous - kind of electricity in nature, but sometimes static electricity causes things to stick together.
Electricity can be dangerous, especially around water because water is a form of conductor as it has impurities like salt in it. Since the nineteenth century, electricity has been used in every part of our lives. Until then, it was just a curiosity seen in a thunderstorm.
Electricity can be created if a magnet passes close to a metal wire. This is the method used by a generator. The biggest generators are in power stations. Electricity can also be generated by combining chemicals in a jar with two different kinds of metal rods. This is the method used in a battery. Static electricity is created through the friction between two materials - for instance a wool cap and a plastic ruler. This may make a spark. Electricity can also be created using energy from the sun, as in photovoltaic cells.
Electricity arrives at homes through wires from the places where it is made. It is used by electric lamps, electric heaters, etc. Many appliances such as washing machines and electric cookers use electricity. In factories, electricity powers machines. People who deal with electricity and electrical devices in our homes and factories are called "electricians".
How it worksEdit
How electricity works can be explained by physics. There are two types of electric charges that push and pull on each other: positive charges and negative charges.
Electric charges push or pull on each other if 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.
It works like magnets, and in fact, electricity creates a magnetic field, in which similar charges repel each other and opposite charges attract. This means that if you put two negative close together and let them go, they would move apart. The same is true for two positive charges. But if you put a positive charge and a negative charge close together, they would pull towards each other. A short way to remember this is the phrase opposites attract, likes repel.
All the matter in the universe is made of tiny positive and negative charges. The positive charges are called protons, and the negative charges are called electrons. Protons are much 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. They are too small to see. Any big object, like your finger, has more atoms and molecules in it than anyone can count. We can only estimate how many there are.
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.
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. Copper is found in electrical wires. But sometimes, other materials are used.
Inside a conductor, electrons bounce around, but they do not keep going in one direction for long. 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 an electrical 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 such as 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 an electric 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.
Here are a few terms that a person can come across when studying how electricity works. The study of electricity and how it makes electrical circuits possible is called electronics. There is a field of engineering called electrical engineering, where people come up with new things using electricity. All of these terms are important for them to know.
- Current is the amount of electric charge that flows. When 1 coulomb of electricity moves past somewhere in 1 second, the current is 1 ampere. To measure current at one point, we use an ammeter.
- Voltage, also called "potential difference", is the "push" behind the current. It is the amount of work per electric charge that an electric source can do. When 1 coulomb of electricity has 1 joule of energy, it will have 1 volt of electric potential. To measure voltage between two points, we use a voltmeter.
- Resistance is the ability of a substance to "slow" the flow of the current, that is, to reduce the rate at which the charge flows through the substance. If an electric voltage of 1 volt maintains a current of 1 ampere through a wire, the resistance of the wire is 1 ohm - this is called Ohm's law. When the flow of current is opposed, energy gets used or gets converted to other forms (such as light, heat, or sound)
- Electric energy is the ability to do work by means of electric devices. Electric energy is a "conserved" property, meaning that it behaves like a substance and can be moved from place to place. Electric energy is measured in joules or kilowatt-hours (kWh).
- Electric power is the rate at which electric energy is being used, stored, or transferred. Flow of electrical energy along power lines are measured in watts. If the electric energy is being converted to another form of energy, it is measured in watts. If some of it is converted and some of it is stored, it is measured in volt-amperes, or if it is stored (as in electric or magnetic fields), it is measured in volt-ampere reactive.
Electricity is mostly generated in places called power stations. Most power stations use heat to boil water into steam which turns a steam engine. The steam engine's turbine turns a machine called a 'generator'. Coiled wires inside the Generator are made to spin in a magnetic field. This causes electricity to flow through the wires. This process is called Electromagnetic induction . Michael Faraday discovered how to do this.
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.