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A magnetic field (sometimes called B-field [1]) is a physical field that describes the magnetic influence on moving electric charges, electric currents, [2]: ch1 [3] and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field.
Similarly, if only the magnetic field (B) is non-zero and is constant in time, the field is said to be a magnetostatic field. However, if either the electric or magnetic field has a time-dependence, then both fields must be considered together as a coupled electromagnetic field using Maxwell's equations .
The magnetic field (B, green arrow) of the magnet's North pole N is directed down in the −y direction. The magnetic field exerts a Lorentz force on the electron (pink arrow) of F 1 = −e(v × B), where e is the electron's charge. Since the electron has a negative charge, from the right hand rule this is directed in the +z direction.
The magnetic flux density (also called magnetic B field or just magnetic field, usually denoted by B) is a vector field. The magnetic B field vector at a given point in space is specified by two properties: Its direction, which is along the orientation of a compass needle. Its magnitude (also called strength), which is proportional to how ...
(in SI units) where ∇ × is the curl operator and again E(r, t) is the electric field and B(r, t) is the magnetic field. These fields can generally be functions of position r and time t. [26] The Maxwell–Faraday equation is one of the four Maxwell's equations, and therefore plays a fundamental role in the theory of classical electromagnetism.
the magnetic field B changes (e.g. an alternating magnetic field, or moving a wire loop towards a bar magnet where the B field is stronger), the wire loop is deformed and the surface Σ changes, the orientation of the surface dA changes (e.g. spinning a wire loop into a fixed magnetic field), any combination of the above
The position and current at any point in the wire are "true" vectors, but the magnetic field B is a pseudovector. [ 1 ] In physics and mathematics , a pseudovector (or axial vector ) [ 2 ] is a quantity that behaves like a vector in many situations, but its direction does not conform when the object is rigidly transformed by rotation ...
The magnetic moment also expresses the magnetic force effect of a magnet. The magnetic field of a magnetic dipole is proportional to its magnetic dipole moment. The dipole component of an object's magnetic field is symmetric about the direction of its magnetic dipole moment, and decreases as the inverse cube of the distance from the object.