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Assume we went to construct an induction motor and we use permanent magnet and you may know that DC current is not supply in this case (rotor is made from only shorted copper or other bars).

  1. Can change of flux be produced on the rotor?

  2. According to Faraday's Law, you will get a current in a coil when the amount of magnetic flux linked with the coil changes. But in case of the permanent magnet, your field is fixed. My question is do can a permanent magnets generate electric current in induction motors?

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3 Answers 3

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You can move your permanent magnet relatively to the rotor. That would change the flux that passes through the coil, since the magnetic field generated by the permanent magnet depends on the distance from the magnet.

Electric current generated by moving permanent magnet

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The magnet is fixed but the rotor is rotating. The field lines that go through the rotor's coils are changing in time, so the flux ist changing too.

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In addition to the answers from chiappette and Gabriel I want to tell you what happens in detail. As long as the direction of the external magnetic field (not matter from a permanent or a electromagnet) an the direction of relative movement between the magnet and a wire are not parallel (they form an area between them) there is induced the movement of charges inside the wire, and this perpendicular and proportional to the mentioned area).

Since a magnetic field couldn't interact with an electric field the interaction takes place with the intrinsic (permanent existing) magnetic dipole moments of the involved charges. The get aligned, by this losing (emitting) photons and get pushed forwards in the wire.

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