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Magnetostatics is the study of magnetic fields in systems where the currents are steady (not changing with time). It is the magnetic analogue of electrostatics , where the charges are stationary. The magnetization need not be static; the equations of magnetostatics can be used to predict fast magnetic switching events that occur on time scales ...
The original circuital law only applies to a magnetostatic situation, to continuous steady currents flowing in a closed circuit. For systems with electric fields that change over time, the original law (as given in this section) must be modified to include a term known as Maxwell's correction (see below).
In three dimensions, the derivative has a special structure allowing the introduction of a cross product: = + = + from which it is easily seen that Gauss's law is the scalar part, the Ampère–Maxwell law is the vector part, Faraday's law is the pseudovector part, and Gauss's law for magnetism is the pseudoscalar part of the equation.
A slightly more general [22] [note 9] way of relating the current to the B-field is through Ampère's law: =, where the line integral is over any arbitrary loop and is the current enclosed by that loop. Ampère's law is always valid for steady currents and can be used to calculate the B-field for certain highly symmetric situations such as an ...
The two Maxwell equations, Faraday's Law and the Ampère–Maxwell Law, illustrate a very practical feature of the electromagnetic field. Faraday's Law may be stated roughly as "a changing magnetic field inside a loop creates an electric voltage around the loop". This is the principle behind the electric generator.
The unit of magnetomotive force is the ampere-turn (At), represented by a steady, direct electric current of one ampere flowing in a single-turn loop of electrically conducting material in a vacuum. The gilbert (Gb), established by the IEC in 1930, [1] is the CGS unit of magnetomotive force and is a slightly smaller unit than the ampere-turn.
The current carrying capacity of a conductor, in the context of electric power wiring. ampere The SI unit of electrical current. Ampère's circuital law The mathematical relation between the integral of the magnetic field over some closed curve to the current passing through the region bound by the curve. Ampère's force law
Two current-carrying wires attract each other magnetically: The bottom wire has current I 1, which creates magnetic field B 1. The top wire carries a current I 2 through the magnetic field B 1, so (by the Lorentz force) the wire experiences a force F 12. (Not shown is the simultaneous process where the top wire makes a magnetic field which ...