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This question is just to clarify a problem I am having regarding Lenz-Law. enter image description hereIn the following picture, the magnet comes in the coil and inducing the coil making the bottom of the coil north and is pushing the magnet out.
But if you look at the way the magnetic field is coming out of a magnet, the direction of the magnetic field in the coil should be the other way. Why is that? I can't find a proper answer on the internet or in my textbook. My textbook says it's just not possible because it's not consistent with the law of conservation of energy.

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  • $\begingroup$ The magnetic field due to the magnet is upwards and the magnetic field due to the induced current in the coil is downwards. This configuration of magnetic fields results in a mutual repulsion between magnet and coil. $\endgroup$
    – Farcher
    Jun 9, 2017 at 8:10

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Magnetic fields of a coil and a magnet must have opposite orientations, because if the magnet comes in to to the coil it must be repelled from it.

Let us suppose that it is not the case. The magnet is attracted by the coil and thus accelerates towards it. It is moving faster and faster so the rate of change of the magnetic flux through the coil is increasing. This results in bigger current in the coil and thus a stronger magnetic field and attraction between coil and magnet. But this results in even bigger acceleration of the magnet, faster changing magnetic flux and even bigger current, which results with even stronger attraction and so on. The velocity of the magnet, electric current and magnetic field are increasing very quickly, "exploding" to infinity. This conclusion is obviously not consistent with conservation of energy, and so we arive at Lenz's Law.

It is worth noting, that if the magnet was getting out of the coil, than it would be attracted towards it, and the orientations of the two magnetic fields would be the same.

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