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UNIT 7: Từ tính

Tham khảo tài liệu unit 7: từ tính, kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Magnetism Magnet The first magnets were known as magnetite or loadstone. Magnetic field lines of a bar magnet Magnet Iron filings "map" of the field of a bar magnet Cutting a magnet An interesting characteristic of magnets is that when you cut a magnet into parts, each part will have both N and S poles. Making Magnets Stroking a piece of unmagnetised iron or steel with a known magnet can make it into a magnet. Making Magnets Placing a magnet alongside a non-magnetised steel knitting needle for some time will magnetise it. The Earth – A huge magnet Electric current and magnetism 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. Ferromagnetic material Spinning electrons Domains Magnetic material with domains misaligned Aligned domains makes material highly magnetic Non magnetic material Permanent magnet Demagnetize Heating a piece of magnetized iron or steel strongly in a flame will demagnetize it. Solenoid H = NI/ | Magnetism Magnet The first magnets were known as magnetite or loadstone. Magnetic field lines of a bar magnet Magnet Iron filings "map" of the field of a bar magnet Cutting a magnet An interesting characteristic of magnets is that when you cut a magnet into parts, each part will have both N and S poles. Making Magnets Stroking a piece of unmagnetised iron or steel with a known magnet can make it into a magnet. Making Magnets Placing a magnet alongside a non-magnetised steel knitting needle for some time will magnetise it. The Earth – A huge magnet Electric current and magnetism 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. Ferromagnetic material Spinning electrons Domains Magnetic material with domains misaligned Aligned domains makes material highly magnetic Non magnetic material Permanent magnet Demagnetize Heating a piece of magnetized iron or steel strongly in a flame will demagnetize it. Solenoid H = NI/ L | Magnetism Magnet The first magnets were known as magnetite or loadstone. Magnetic field lines of a bar magnet Magnet Iron filings "map" of the field of a bar magnet Cutting a magnet An interesting characteristic of magnets is that when you cut a magnet into parts, each part will have both N and S poles. Making Magnets Stroking a piece of unmagnetised iron or steel with a known magnet can make it into a magnet. Making Magnets Placing a magnet alongside a non-magnetised steel knitting needle for some time will magnetise it. The Earth – A huge magnet Electric current and magnetism 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. Ferromagnetic material Spinning .