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PERMANENT MAGNET
A permanent magnet is made from steel. As steel has more retentivity than iron, it does not lose its
magnetism easily.
A steel bar is placed inside a solenoid AB as shown in the figure and the current is switched on and
off with help of key K. On removing and testing the bar, it is found to be magnetised. It is of no
use to pass the current through the solenoid for a long time because the bar will not be magnetised
beyond a certain limit. On the other hand, the solenoid may be damaged due to overheating.
Apart from different varieties of steel (carbon steel, chromium steel, cobalt and tungsten steel),
some alloys like Alnico (aluminium, nickel and cobalt) and Nipermag (an alloy of iron, nickel,
aluminum and titanium) are used to make very strong permanent magnets.
