What is Magnetic?
Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the moments of atomic dipoles give rise to a magnetic field, which acts on other currents and dipoles. All materials experience some form of magnetism. Permanent magnets, composed of ferromagnetic materials, cause persistent magnetic fields, while electromagnets use electric current to generate a magnetic field that disappears when the current is turned off. Materials can also be attracted to a magnet (magnetic attraction) or repel it (magnetic repulsion).
How do Magnets Work?
All magnets have north and south poles. Opposite poles are attracted to each other, while the same poles repel each other. When you rub a piece of iron along a magnet, the north-seeking poles of the atoms in the iron line up in the same direction. The force generated by the aligned atoms creates a magnetic field.
A permanent magnet is an object made from certain types of material that creates its own persistent magnetic field even in the absence of an applied external magnetic field. A common example is a bar magnet. Materials that can be Magnetized include: Iron Nickel Cobalt Gadolinium Dysprosium Terbium
Materials that create their own persistent internal magnetic fields are called ferromagnets; those with only weak internal fields are called paramagnets; those with no intrinsicfields are called diamagnets. Ferromagnets respond strongly to external fields whereas paramagnets and diamagnetics only weakly so. Alloys containing various proportions of elements such as iron (Fe), cobalt (Co), nickel (Ni), gadolinium (Gd), dysprosium(Dy), and terbium(Tb) can be carefully designed so as to exhibit very strong ferromagnetism with high coercivity, making them useful for practical applications such as refrigerator magnetsand electric motors.
The strength and directionofa material’s intrinsic Magnetic moment generally determines how it will interact with an external Magneticfield: Ifthe North poleofastrong Magnetis broughtnearoneendofa pieceofiron ,the Northpolesoftheatomsintheringwilllineupinthesamedirection(becoming”aligned”),andviceversaifSouthis broughtnearSouth .ThealignmentwillpersistaslongastheexternalMagnetispresent—EXCEPTthat iftheAlignmentiscreatedinthewrongdirection ,thenAtomicForceswithinironwillworktomaintaintherightdirection . ThisworkrequiresEnergyinput ,whichcanbeprovidedbyHeat .