Question

why should corecivity be low for electromagnets

Answer 1

Therefore the material used in an electromagnet should have low retentivity, so that it doesn't get magnetized, or gets demagnetised easily. Coercivity is the magnetic field intensity needed to reduce the magnetization of a ferromagnetic ...

Answer 2

Electromagnets are used to turn on and off. This is opposed to permanent magnets that are desired to remain magnetic all the time. Low coercivity means that it requires low magnetic field thus low opposite current to bring it back to the non-magnetic state. Low retentivity means that it becomes a weak magnet when the current is turned off, ideally zero retentivity. all of these features are necessary for the typical application: pick up iron-like metals while the current is on and drop them when the current is off.
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