Question
What is an electromagnet?
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Answer
An electromagnet is an insulated coil wrapped around a ferromagnetic core $($usually a soft iron$)$ of high permeability and low retentivity. When a current is passed through the coil$-a$ solenoid or toroid, the ferromagnetic material magnifies the magnetic field of the coil, the magnification factor being the relative permeability$ (\mu / \mu _0)$ of the core. The magnetic field of the current$-$carrying coil magnetizes the core material, thereby producing a much larger field than the coil would produce by itself.
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