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Either an electric current is passed through the wire of the coil to generate a magnetic field, or conversely, an external time-varying magnetic field through the interior of the coil generates an EMF in the conductor. A current through any conductor creates a circular magnetic field around the conductor due to Ampere's law. [3]
In classical electromagnetism, Ampère's circuital law (not to be confused with Ampère's force law) [1] relates the circulation of a magnetic field around a closed loop to the electric current passing through the loop. James Clerk Maxwell derived it using hydrodynamics in his 1861 published paper "On Physical Lines of Force". [2]
where H 0 is the applied magnetic field due only to the free currents and H d is the demagnetizing field due only to the bound currents. The magnetic H-field, therefore, re-factors the bound current in terms of "magnetic charges". The H field lines loop only around "free current" and, unlike the magnetic B field, begins and ends near magnetic ...
The magnetic field of a current loop. The ring represents the current loop, which goes into the page at the x and comes out at the dot. In classical physics, the magnetic field of a dipole is calculated as the limit of either a current loop or a pair of charges as the source shrinks to a point while keeping the magnetic moment m constant.
In more visual terms, the magnetic flux through the wire loop is proportional to the number of magnetic field lines that pass through the loop. When the flux changes—because B changes, or because the wire loop is moved or deformed, or both—Faraday's law of induction says that the wire loop acquires an emf , defined as the energy available ...
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 ...
The application of this law implicitly relies on the superposition principle for magnetic fields, i.e. the fact that the magnetic field is a vector sum of the field created by each infinitesimal section of the wire individually. [6] For example, consider the magnetic field of a loop of radius carrying a current .
Magnetic field (green) induced by a current-carrying wire winding (red) in a magnetic circuit consisting of an iron core C forming a closed loop with two air gaps G in it. In an analogy to an electric circuit, the winding acts analogously to an electric battery, providing the magnetizing field , the core pieces act like wires, and the gaps G act like resistors.