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I just started learning about magnetic fields by myself. In my textbook it says that the magnitude or intensity of induction of a magnetic field is equal to the amount of field lines that pass through a surface facing the direction of $B$. So as I understand it $B$ causes some magnetic objects (compass in this example) to re-oriente themselves and logically the more field lines the larger $B$ will be and the more this object will tend to turn itself. $H$ is later defined as $B/\mu$ effectively removing the magnetic permittivity of a vacuum giving us the "strength" of the field at that point.

Can someone tell me the difference between $B$ and $H$ as they seem to be both referencing the strength and also tell me how dividing by the permittivity of free space gives us the "strength" of the field. Also my text book sometimes calls them forces eventhough none of them at in newtons ;-;

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  • $\begingroup$ this may help physics.stackexchange.com/questions/779074/… $\endgroup$
    – hyportnex
    Commented Sep 8, 2023 at 15:52
  • $\begingroup$ This is incorrect:’ In my textbook it says that the magnitude or intensity of induction of a magnetic field is equal to the amount of field lines that pass through a surface facing the direction of B.’ Field lines are just for illustration of the field strength and direction. $\endgroup$
    – my2cts
    Commented Jul 16 at 10:35

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In standard units and in vacuum, it'just a tradition to distinguish fields and induction, only E and B are necessary in equations. In materials, there are magnetic and electric polarization effects, and so material-specific magnetic and dielectric constants become a way to model that, and difference between fields and inductions just helps with boundary conditions.

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  • $\begingroup$ As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center. $\endgroup$
    – Community Bot
    Commented Sep 8, 2023 at 13:35

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