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Iron filings used to show the magnetic field lines of a bar magnet. In the history of physics, the concept of fields had its origins in the 18th century in a mathematical formulation of Newton's law of universal gravitation, but it was seen as deficient as it implied action at a distance.
Now Maxwell logically showed how these methods of calculation could be applied to the electro-magnetic field. [126] The energy of a dynamical system is partly kinetic, partly potential. Maxwell supposes that the magnetic energy of the field is kinetic energy, the electric energy potential. [127]
1888 – Introduction of the induction motor, an electric motor that harnesses a rotating magnetic field produced by alternating current, independently invented by Galileo Ferraris and Nikola Tesla. Albert Einstein in the patent office, Bern Switzerland, 1905
The magnetic field lines are indicated, with their direction shown by arrows. The magnetic flux corresponds to the 'density of field lines'. The magnetic flux is thus densest in the middle of the solenoid, and weakest outside of it. Faraday's law of induction makes use of the magnetic flux Φ B through a region of space enclosed by a wire loop.
He examined the nature of both electric and magnetic fields in his two-part paper "On physical lines of force", which was published in 1861. In it, he provided a conceptual model for electromagnetic induction, consisting of tiny spinning cells of magnetic flux. Two more parts were later added to and published in that same paper in early 1862.
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 magnetic field of permanent magnets can be quite complicated, especially near the magnet. The magnetic field of a small [note 6] straight magnet is proportional to the magnet's strength (called its magnetic dipole moment m). The equations are non-trivial and depend on the distance from the magnet and the orientation of the magnet.
To concentrate the magnetic field in an electromagnet, the wire is wound into a coil with many turns of wire lying side-by-side. [2] The magnetic field of all the turns of wire passes through the center of the coil, creating a strong magnetic field there. [2] A coil forming the shape of a straight tube (a helix) is called a solenoid. [1] [2]