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The magnetic field is often created by a current-carrying coil of wire around the core. The use of a magnetic core can increase the strength of magnetic field in an electromagnetic coil by a factor of several hundred times what it would be without the core. However, magnetic cores have side effects which must be taken into account.
A coil with a core which is a straight bar or other non-loop shape is called an open-core coil. This has lower magnetic field and inductance than a closed core, but is often used to prevent magnetic saturation of the core. A coil without a ferromagnetic core is called an air-core coil. [14]
Much stronger magnetic fields can be produced if a magnetic core, made of a soft ferromagnetic (or ferrimagnetic) material such as iron, is placed inside the coil. [ 1 ] [ 2 ] [ 15 ] [ 16 ] A core can increase the magnetic field to thousands of times the strength of the field of the coil alone, due to the high magnetic permeability μ ...
When the pair of two electromagnets of a Helmholtz coil carry an equal electric current in the opposite direction, it is known as anti-Helmholtz coil, which creates a region of nearly uniform magnetic field gradient, and is used for creating magnetic traps for atomic physics experiments.
For a magnetic circuit constructed with an air gap or air gaps, the permeability of a hypothetical homogeneous material which would provide the same reluctance; (these "effective" above are sizes of a toroid core made from the same material which has the same magnetic properties as the core); Minimum cross-section, A min; Inductance factor, A L
Paramagnetic materials are attracted to magnetic fields, hence have a relative magnetic permeability greater than one (or, equivalently, a positive magnetic susceptibility). The magnetic moment induced by the applied field is linear in the field strength, and it is rather weak. It typically requires a sensitive analytical balance to detect the ...
The magnetic field of the coil magnetizes the material of the core, aligning its magnetic domains, and the magnetic field of the core adds to that of the coil, increasing the flux through the coil. This is called a ferromagnetic core inductor. A magnetic core can increase the inductance of a coil by thousands of times.
A field coil is an electromagnet used to generate a magnetic field in an electro-magnetic machine, typically a rotating electrical machine such as a motor or generator. It consists of a coil of wire through which the field current flows. In a rotating machine, the field coils are wound on an iron magnetic core which