Electricity
Everything is made up of atoms. Each one of them has three particles : protons, neutrons and electrons. Electrons spin around the centre of an atom. They have a negative charge. Protons, which are in the centre of atoms, have a positive charge.
Normally, an atom has as many protons as it has electrons. It is stable or balanced. Carbon, for example has six protons and six electrons.
Scientists can make electrons travel from one atom to another. An atom that loses electrons is positively charged, an atom that gets more electrons is negatively charged.
Electricity is created when electrons move between atoms. Positive atoms look for free negative electrons and attract them, so that they can be balanced.
Conductors and Insulators
Electricity can pass through some objects better than through others. Conductors are materials through which electrons can travel more freely. Copper, aluminium, steel and other metals are good conductors. So are some liquids like saltwater.
Insulators are materials in which electrons cannot move around. They stay in place. Glass, rubber, plastic or dry wood are good insulators. They are important for your safety, because without them, you couldn’t touch a hot pan or plug in a TV set.
Electric Current
When electrons move through a conductor an electric current is created. A current that always flows in one direction is called a direct current (DC). A battery for example, produces a direct current. A current that flows back and forth is called an alternating current (AC).
Electric Circuits
Electrons cannot jump freely through the air to a positively charged atom. They need a circuit to move. When a source of energy, like a battery, is connected to a light bulb the electrons can move from the battery to the light bulb and back again. We call this an electric circuit.
Sometimes there are many circuits in an electrical device that make it work. A TV set or a computer may have millions of parts that are connected to each other in different ways.
You can stop the current from flowing by putting a switch into the circuit. You can open the circuit and stop electrons from moving.
A piece of metal or wire can also be used to produce heat. When an electrical current passes through such metal it can be slowed down by resistance. This causes friction and makes the wires hot. That’s why you can toast your bread in a toaster or dry your hair with warm air from a hairdryer.
In some cases wires can become too hot if too many electrons flow through them. Special switches ,called fuses, protect the wiring in many buildings .
Kinds of electricity
Static electricity
- happens when there is a build-up of electrons
- it stays in one place and then jumps to an object
- it does not need a closed circuit to flow
- it is the kind of electricity you feel when you rub your pullover against an object or when you drag your feet over a carpet.
- lightning is a form of static electricity
Current electricity
- happens when electrons flow freely between objects
- it needs a conductor—something in which it can flow , like a wire.
- current electricity needs a closed circuit
- it is in many electrical appliances in our homes - toasters, TV sets , computers.
- a battery is a form of current electricity
How batteries work
A battery has liquid or paste in it that helps it produce electric charges. The flat end of the battery has a negative charge and the end with the bump has a positive charge.
When you link a wire between both ends a current flows. When the current passes through a light bulb electric energy is converted into light.
The chemicals in the battery keep the ends charged and the battery going. As times passes, the chemical becomes weaker and weaker and the battery cannot produce any more energy.
How electricity is produced
Generators are used to transform mechanical energy into electrical energy. A magnet rotates inside a coil of wire. When the magnet moves, an electric current is produced in the wire.
Most power stations use turbines to make the generator rotate. Water is heated to make steam , which pushes the blades of the turbine. Gas, oil or coal can be used to heat the water. Some countries build power stations on rivers, where the moving water pushes the turbine blades.
How electricity is measured
Electricity is measured in watts, named after James Watt who invented the steam engine. It would take about 750 watts to equal one horsepower.
A kilowatt-hour is the energy of 1,000 watts that work for one hour. If, for example, you use a 100-watt light bulb for 10 hours you have used 1 kilowatt of electricity.
How electricity is transported
The electricity produced by a generator travels along cables to a transformer that changes the voltage of electricity. Power lines carry the high-voltage electricity over very long distances. When it reaches your home town another transformer lowers the voltage and smaller power lines bring it to homes, offices and factories.
Electrical safety
It is important to understand why and how you can protect yourself from electrical injuries.
Electric shock occurs when an electric current passes through your body. It can lead to heart failure and can damage other parts of your body. It can also burn your skin and other body tissues.
A very weak electrical object, like a battery, cannot do any harm to you, but inside the house you have devices and machines that use 220 volts.
Most machines in your house have safety features to protect you. It something goes wrong, a special wire leads the electricity to the ground where nothing can happen.
There are also electrical dangers outside your house. Trees that touch power lines can be dangerous. Lightning has more than enough electricity to kill a person. If you get caught in a thunderstorm stay away from open fields and high places. One of the safest places is your car, because lightning will only hit the outside metal of the car.
Downloadable PDF Text- and Worksheets
Related Topics
Words
- appliance = an electrical machine that you normally use in the house, like a cooker or a washing machine
- attract = pull towards an object
- back and forth = to go in one direction and then in the other
- balanced = the same as stable
- blade =a flat part of an object that pushes against water
- build-up = increase
- bump = a small area that is higher than the rest
- carbon = a chemical material that is in coal or petrol. It is in its purest form in diamonds
- charge =the electricity that is put into an object ,like a battery, to give it power
- circuit =the complete circle that an electric current travels
- coil =a wire that goes around an object in a circle and produces light or heat when electricity passes through
- connect = join
- convert = change
- copper = a soft red and brown metal that lets electricity and heat pass through easily
- cord =cable
- current = a flow of electricity through a piece of metal
- current = a flow of electricity through a piece of metal
- decrease = to become smaller
- device = machine or a tool that does something special
- distribution lines =wires or cables that transport electricity
- drag = pull
- equal = the same as
- flow = to move
- friction = when you rub something against something else it gets hot
- fuse = a short piece of wire inside a machine which stops the electricity when there is too much power
- heart failure = when your heart stops beating
- high voltage =a high electrical force
- in place = where they are
- increase = to become bigger
- injury =if you hurt yourself
- keep = remain, stay
- light bulb = a glass object that is inside a lamp . It produces light
- lightning =a powerful flash of light in the sky, during a thunderstorm
- liquid =fluid, watery object
- measured =the unit of something
- occur = happen
- pan = a round metal container that you use for cooking
- particle = a very small part of an atom
- pass through = go through
- paste = sticky Stuff , like glue
- plug in =to connect an electrical object to the electricity supply of a house
- power line = a large wire that carries electricity above or under the ground
- resistance =material that stops electricity going through it
- rotate = to go around
- safety =security, protection
- safety feature =things in machines or electric objects that protect you from being hurt
- scientist =a person who is trained in science
- socket =a place in a wall where you can connect an electrical object to the main supply of electricity
- source = the place you get something from
- spin = to turn around something very quickly
- steam = the white gas that water produces when you make it hot
- steam engine = an engine or motor that works with steam power
- steel = a strong metal that can be formed
- switch = an object that starts or stops the flow of electricity when you press it
- tissue =the material that forms animal or plant cells
- transform = change
- transformer = a machine that changes electricity from one voltage to another
- turbine = a motor that moves a special wheel around
- voltage =an electrical force measured in volts
- wire = a very thin piece of metal in which electricity can pass through
- wiring =the network of wires in a house or building