www.themegallery .com Magnet The first magnets were known as magnetite or loadstone... Magnetic field lines of a bar magnet... www.themegallery .com Magnet Iron filings "map" of the fi
Trang 1Magnetism
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Magnet
The first magnets were
known as magnetite
or loadstone
Trang 3Magnetic field lines of a bar magnet
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Magnet
Iron filings "map" of the field of a bar magnet
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Trang 7July 29, 2014
Cutting a magnet
when you cut a magnet into parts, each part will have both N and S poles.
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Making Magnets
Stroking a piece of unmagnetised iron or steel with a known magnet can make it into a magnet
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Making Magnets
Placing a magnet alongside a non-magnetised steel knitting needle for some time will magnetise it.
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The Earth – A huge magnet
Trang 11Electric current and magnetism
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Classification of materials
Ferromagnetic materials
strongly attracted by a magnetic force:
iron (Fe), nickel (Ni), cobalt (Co) and gadolinium (Gd)
Paramagnetic materials
weakly attracted to magnets: Aluminum
Diamagnetic materials
when they are exposed to a strong magnetic field, they induce a weak
magnetic field in the opposite direction
Trang 13Ferromagnetic material
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Spinning electrons
Trang 15Magnetic material with domains misaligned
Aligned domains makes material highly magnetic
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Trang 17Non magnetic material
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Permanent magnet
Trang 19Heating a piece of magnetized iron or steel strongly in a flame will
demagnetize it
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Solenoid
H = NI/ L