Question

Why magnetic length is equal to 5/6 times of geometric length?

Answer 1

The magnetic field lines begin spreading apart shortly before they reach the physical end of the magnet. As such, at the physical end of the magnet, the number of magnetic field lines per unit area is slightly less. You must travel about 8% into the magnet, from each end, to find the magnetic field at very near full strength.

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@KHUSHALI. ...