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
Nội dung trích xuất từ tài liệu:
UNIT 7: Từ tínhLOGO www.themegallery.com MagnetismLOGO Magnet The first magnets were known as magnetite or loadstone.LOGO Magnetic field lines of a bar magnetLOGO Magnet Iron filings map of the field of a bar magnetLOGOLOGOLOGO 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.June 6, 2011LOGO Making Magnets Stroking a piece of unmagnetised iron or steel with a known magnet can make it into a magnet.LOGO Making Magnets Placing a magnet alongside a non- magnetised steel knitting needle for some time will magnetise it.LOGO The Earth – A huge magnetLOGO Electric current and magnetismLOGO 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.LOGO Ferromagnetic materialLOGO Spinning electronsLOGO Domains Magnetic material with domains misaligned Aligned domains makes material highly magneticLOGOLOGO Non magnetic materialLOGO Permanent magnetLOGO Demagnetize Heating a piece of magnetized iron or steel strongly in a flame will demagnetize it.LOGO Solenoid H = NI/ L