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Magnetic Field lines

  1. Jan 6, 2014 #1
    Hello All,

    I was just checking magnetic field lines as in attached figure.

    I am curious to see some gaps between adjecent field lines in the figure.
    Why it is not like a sheath( for example in lighting field) but as lines?

    Thanx in advance


    Attached Files:

  2. jcsd
  3. Jan 6, 2014 #2
    There is actually a continuum of field lines, but only a finite number of discrete lines can be visualized by this method.

    Others will probably give more knowledgeable answers, but I suspect that the gaps between the lines of iron fillings are caused by magnetic forces between the fillings themselves.
  4. Jan 6, 2014 #3


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    Field lines are only a 'construct' to give an idea what the field is doing. There are alternative ways of showing the field. You can write pairs of numbers on a regular grid (magnitude and direction of the magnetic field vector) or you can draw contours of equal potential - but we are not familiar with that way. The spacing between the lines gives an indication of the strength of the field - close together means strong.
    When you do the trick with iron filings, the tiny bits of iron actually affect the local H field strength and produce a local B field. This means they tend to stick together in chains. It's a stunning demonstration but you shouldn't read too much into what you see - or expect to get a 'measurement' out of the picture.
    The 'holes' in the picture are where the field is too low for the filings to stick together.
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