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B and H?

  1. Mar 12, 2008 #1
    Why don't we call B magnetic field strength like we call E, the electrical counterpart. In stead we call it magnetic induction which is less descriptive.
  2. jcsd
  3. Mar 12, 2008 #2


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    That is due to the intenational conferences the "named" physical quantities and invented SI. Unfortunately, there was a split in the '50s between physicists and (mostly industrial) engineers. The engineers were most interested in magnetic flux, which powered their generators. They invented the Weber of flux and called B "magnetic flux density" in units of Weber per square meter. That name was unwieldy, even for them, so someone suggested the strange term "magnetic induction". The engineers were careful not to give B the same name as E, so as not to confuse the two. Physicists know it is no confusion, after Maxwell and Einstein, that E and B are just different components of the same tensor. Several advancedl EM texts call B the magnetic field as you and I suggest.
    These books also use the same unit, gauss, for B and E, in gaussian units.
  4. Mar 12, 2008 #3
    The problem is that, as soon as you look at material properties, B is not a good descriptor of magnetic field strength, which is better described by H.
  5. Mar 12, 2008 #4
    I'm not sure what you mean by "counterpart"? "E" has units of volts/meter, and is the electric field intensity. "H" has units of amps/meter and is called magnetic field intensity. It appears that E and H are "counterparts". Also, at a boundary of 2 different materials, the "normal" (perpendicular) components of "B" in both materials, and that of "D" in both are equal. But, the tangential components of "E" are equal for both materials, as well as that of "H".

    It is obvious that "B" is the counterpart of "D", the electric flux density, aka "electric displacement", whereas "H" is the counterpart of "E".

    I hope this helps. BR.
    Last edited: Mar 12, 2008
  6. Mar 14, 2008 #5
    see B is magnetic induction which gives effect of magnetic field H .they both look like same macroscopicaly but on a smaller scale there is a huge diff. b/w them just like there is b/w E and D.
    B will also depend on the medium while H does not.
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