Natural science unit 5
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ceiatinasacristan
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Natural science unit 5
Magnetism:
Magnets:
They can be natural or man-made.
The mineral magnetite is a natural magnet.
Magnetic metals:
iron.
nickel.
cobalt.
Types of magnets:
Permanent magnets:
never lose their magnetism.
Induced magnets or temporary magnets:
have a temporary magnetic force.
Poles:
All magnets have two poles:
north.
south.
If you put a magnet in water for example, it will point to the Earth´s magnetic north pole.
opposite poles:
attract.
same poles:
repel.
Magnetic field:
It is the area around a magnet.
We can´t see this field, but we can see its shape using iron filings.
The magnetic field is strongest at the poles.
The Earth is a magnet:
The earth´s molten iron core acts like a magnet.
The magnetic north pole is a slight angel away from the geographical North Pole.
The magnetic field around the Earth deflects cosmic rays and protects our atmosphere.
Compass:
It is a navigational instrument.
It has a needle that is magnetised and points to the magnetic North Pole.
The rose is marked with the cardinal points.
Were first used in medieval times.
Magnets and electromagnets:
Magnetic materials:
are always metallic, but not all metals are attracted to magnts.
Electromagnets:
are objects that act like magnets when an electrical current passs through them.
the magnet is activated by electricity, if you swich off the electrical current , the magnet stops working.
Magnets all around us:
We use magnets every day.
Electromagnets are used in:
motors.
generators.
electric bells.
loudspeakers.
the hard disks of a computer.
Magnets are used for magnetic separation and for lifting heavy metal objects.
maglev trains use magnetic levitation to move without touching the ground.