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The magnetic pole model assumes that the magnetic forces between magnets are due to magnetic charges near the poles. This model works even close to the magnet when the magnetic field becomes more complicated, and more dependent on the detailed shape and magnetization of the magnet than just the magnetic dipole contribution.
Electricity and magnetism were originally considered to be two separate forces. This view changed with the publication of James Clerk Maxwell 's 1873 A Treatise on Electricity and Magnetism [ 6 ] in which the interactions of positive and negative charges were shown to be mediated by one force.
Glazed frame, containing "Delineation of Lines of Magnetic Force by Iron filings" prepared by Michael Faraday. Michael Faraday was the first who suggested that action at a distance was inadequate as an account of electric and magnetic forces, even in the form of a (mathematical) potential field.
The magnetic Lorentz force v × B drives a current along the conducting radius to the conducting rim, and from there the circuit completes through the lower brush and the axle supporting the disc. This device generates an emf and a current, although the shape of the "circuit" is constant and thus the flux through the circuit does not change ...
The magnetic field produced by the magnet then is the net magnetic field of these dipoles; any net force on the magnet is a result of adding up the forces on the individual dipoles. There are two simplified models for the nature of these dipoles: the magnetic pole model and the Amperian loop model .
Lorentz force on a charged particle (of charge q) in motion (velocity v), used as the definition of the E field and B field. Here subscripts e and m are used to differ between electric and magnetic charges .
L – average length of the magnetic circuit (used in Eq. 3). It is the sum of the length L core in the iron core pieces and the length L gap in the air gaps G. Both the leakage flux and the fringing fields get larger as the gaps are increased, reducing the force exerted by the magnet.
Electromagnetic or magnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field. Michael Faraday is generally credited with the discovery of induction in 1831, and James Clerk Maxwell mathematically described it as Faraday's law of induction .