This is an electromagnet: a device in which an electric current produces the magnetic field. This is because ferromagnetic metals like iron already contain small magnetic fields inside their bulk produced by its atoms. When the iron is used as the core in an electromagnet and a current is passed, the magnetic field it produces penetrates the iron’s bulk and forces the tiny fields to align along the external field’s direction. In a superconducting electromagnet, such as in an MRI, superconducting wire is coiled around a core to produce magnetic fields of up to 30 tesla (600,000-times as powerful as the earth’s). In Bitter electromagnets, current flows in wires coiled through a helical stack of electromagnets, producing magnetic fields of up to 40 tesla.

Source: The Hindu June 17, 2024 15:59 UTC