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In electromagnetics, the term magnetic field is used for two distinct but closely related vector fields denoted by the symbols B and H. In the International System of Units, the unit of B, magnetic flux density, is the tesla (in SI base units: kilogram per second squared per ampere), [5]: 21 which is equivalent to newton per meter per ampere.
Paramagnetic materials have a weak induced magnetization in a magnetic field, which disappears when the magnetic field is removed. Ferromagnetic and ferrimagnetic materials have strong magnetization in a magnetic field, and can be magnetized to have magnetization in the absence of an external field, becoming a permanent magnet .
The magnetic moments of objects are typically measured with devices called magnetometers, though not all magnetometers measure magnetic moment: Some are configured to measure magnetic field instead. If the magnetic field surrounding an object is known well enough, though, then the magnetic moment can be calculated from that magnetic field.
A good magnetic core material must have high permeability. [35] For passive magnetic levitation a relative permeability below 1 is needed (corresponding to a negative susceptibility). Permeability varies with a magnetic field. Values shown above are approximate and valid only at the magnetic fields shown.
Measure for how the magnetization of material is affected by the application of an external magnetic field H/m L M T −2 I −2: intensive Permittivity: ε s: Measure for how the polarization of a material is affected by the application of an external electric field F/m L −3 M −1 T 4 I 2: intensive Plane angle: θ: Ratio of circular arc ...
Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other.Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, magnetism is one of two aspects of electromagnetism.
The definitions for monopoles are of theoretical interest, although real magnetic dipoles can be described using pole strengths. There are two possible units for monopole strength, Wb (Weber) and A m (Ampere metre). Dimensional analysis shows that magnetic charges relate by q m (Wb) = μ 0 q m (Am).
When charged particles move in electric and magnetic fields the following two laws apply: Lorentz force law: = (+),; Newton's second law of motion: = =; where F is the force applied to the ion, m is the mass of the particle, a is the acceleration, Q is the electric charge, E is the electric field, and v × B is the cross product of the ion's velocity and the magnetic flux density.