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Year 7 & 8 TOC


Magnetic forces

LO: Investigating the effects of applying different forces to familiar object

A magnetic forces are all around us. In fact, the Earth has it’s own magnetic field. This is how a compass works. The compass needle lines up with the Earth’s magnetic field. The N points to the north magnetic pole of the Earth. This is different from the north pole tho. The magnetic north pole is 100’s of milometers from the geographical north pole. Magnets clearly play a big part in our life. So, how do they work? 

When turtles hatch they crawl down the beach to the water. From there they swim through the oceans. Eventually, when they are ready to mate and lay their eggs, they use the Earth’s magnetic field to guide them back to the same beach they hatched from. There they will mate and lay their eggs!

Source: New York Times

What are they made of?

Magnets are made of a mixture of metals (mostly iron), this makes them an alloy. The ones we use in class are a mixture of aluminium, nickel, cobalt and iron. Some new magnets are made of rare earth metal. They are much stronger and don’t loose their magnetism over time. Magnets which don’t loose their magnetism over time are called permanent magnets. 

Attraction & repulsion

You’ll notice that a magnet has a north and south side. This is their magnetic poles. If you place a north pole and a south pole of 2 different magnets next to each other they will attract. This is called an attraction force
If you place the same poles next to each other (north and north), they will push each other away without touching each other. This is known as repulsion force

Magnetic domains

Magnets are made up of molecules, that are uniquely arranged to all line up. Large sections of these molecules are called domains, when these domains point in the same direction, we get a magnetic field.
You can make an iron nail magnetic by sliding a magnet along one side of it in one direction. This causes all the domains that were previously pointing in different directions, to point in the same direction. Dropping this nail tho, causes the domains to become random again.
Permanent magnets, have their domains arranged while they are buried deep in the ground. If you break these magnets in half, their domains arrangement don’t change and you end up with 2 magnets. 

Maglev trains rely on magnetic properties. The push force created from the magnets allow the train to hover above the tracks. The driver of the train changes the poles of the train’s magnets to push it forward. Since the train is hovering above the tracks there’s no friction. They can reach up to 603 km/h!

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