Magnets and Magnetism
A magnet is a piece of rock or metal that can pull other metals towards it. The force of magnets is called magnetism. Together with gravity and electricity it is a basic force of nature. Early humans discovered magnets and magnetism thousands of years ago. They found out that certain types of rock, called loadstone, pulled iron and other metal objects towards it. After some time they found out that thin pieces of such a rock would always point in one direction if you hung it on a piece of thread . The ends of such a metal are the poles of a magnet. All magnets have a magnetic field around them, the force between the two poles.
Magnets attract or repel other metals. This is because every magnet has two poles: a north and a south pole. North and south poles attract each other but two north poles or two south poles push each other apart.
Our planet is also a big magnet with a North and a South Pole. But the Earth’s magnetic poles are not in the same place as the geographic poles. The magnetic North Pole, for example, is in northern Canada. Compasses always point to the magnetic poles, not to the geographic ones.
Magnetism comes from electrons , the tiny particles that fly around the nucleus of an atom. They are negatively charged and produce a very weak magnetic field. When many of these electrons point towards the same direction they can pull metals to them.
It is also possible to make a magnet by taking an existing one and rubbing another piece of metal with it. If you keep rubbing the new piece of metal in the same direction its electrons will start to point in that direction , thus creating a new magnet.
If a magnet keeps its magnetic field all the time we call it a permanent magnet. However , not all magnets are permanent . Some objects become magnets only when electricity passes through them. They are called electromagnets. There are many examples of such electromagnets in everyday life: car motors, railway signals, loudspeakers .
Magnetism and electricity
In the 1700s scientists discovered that magnetism and electricity had similar features. Just like magnets have two poles, electricity has positive and negative charges . A positive and a negative charge attract each other and two negative or two positive charges repel each other.
After they had found this out they started making useful tools and machines with the help of electricity and magnetism. The Danish physicist Oersted sent electricity through a wire and put a compass near it. To his surprise the compass needle moved. Soon after that the first electromagnet was made by making a wire into a coil and sending electricity through it.
Use of magnets
The first magnetic instruments were compasses which sailors used to guide them on their journeys . Today, magnets can be found in many areas of everyday life. They are in washing machines, hold doors shut and work in generators and electric motors. Credit cards have magnetic strips on them that give you financial information. Magnetic audio and videotapes as well as disks have many tiny magnetic particles which are used to store sounds, pictures and other information.
In medicine a magnetic resonance imaging machine (MRI) can create exact pictures of organs and bones inside the human body . It is much better and more exact than x-rays .
Powerful electromagnets are attached to big cranes that can move iron and steel. In some parts of the world trains travel on tracks that are magnetized . These trains, called maglev, are lifted above the tracks and do not have any contact with them. They travel at speeds of up to 480 km an hour.
Magnets in animals
Scientists have also discovered that some animals, like pigeons , dolphins and turtles may have some magnetic particles in their body. They are able to detect the Earth’s magnetic field and find out their location.
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Words
- attach = connect
- attract = to pull an object towards another one
- basic = important, main
- charge =electricity that is put into a battery or another electrical object
- coil =a wire that is wound in a circle ; when electricity passes through it it gives you light or heat
- crane = a tall machine that is used to lift heavy things
- create = make
- credit card = small plastic card that you use to buy things and pay for them later
- detect = find
- direction =way , course
- discover = to find out for the first time
- dolphin = a very intelligent sea animal like a fish with a long grey pointed nose
- electricity =the power that is carried by wires and cables to make machines work or give light or heat
- electron = a very small particle that moves around the nucleus of an atom
- force = power
- generator =machine that produces electricity
- gravity = the power that makes something fall down to Earth
- guide = lead
- hang—hung =fall from an object
- however =but
- journey = a long trip
- lift = raise
- lodestone = a piece of iron that acts like a magnet
- loudspeaker = something that makes sounds louder
- magnetize = to make iron or steel able to pull other pieces of metal towards itself
- needle =pointer
- particle =very, very small element of something
- permanent = something that lasts forever
- pigeon = a grey bird with short legs that you can often find in cities
- point = show
- repel = to push an object away from another one
- rub = to press your hand backward and forward over an object
- sailor = a person who works and lives on a ship
- scientist =a person who is trained in science
- speed =how fast something is
- store = to keep facts and information in a place for a longer time
- strip =narrow piece
- thread = a long thin string of cotton
- thus =therefore, that is why
- tiny = very, very small
- tool = something that does a certain job
- towards = in the direction of
- track = two metal lines on which trains travel
- turtle = a reptile that lives mostly in water and has a hard shell
- useful = helpful
- videotape =material that you record pictures and sounds on
- weak = not very strong
- wire = a very thin piece of metal through which electricity travels
- x-rays = rays that can go through objects of your body and can be used for taking pictures of inside organs