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Homework Help: Direction of field inside and outside a magnetic dipole

  1. Feb 13, 2007 #1
    1. The problem statement, all variables and given/known data
    1) In the case of a bar magnet, outside it, the magnetic lines of forces start from North Pole and end on South Pole. But inside it, the lines of force start from south and end on North Pole. According to definition of direction of lines of force, it is the direction in which a unit north pole would move when placed in a magnetic field. This is true outside the bar magnet but not so inside it. Is the rule applicable only outside the body of the bar magnet?
    2) Now, it is a known fact that a circular current carrying conductor acts like a magnetic dipole(bar magnet). If on placing the coil with one of its side facing you, and the current flows in clockwise direction, then that side acts like a south pole and the other side acts like North Pole. At the centre of the coil, will the direction of field be from north to south or south to North Pole? I have this doubt because inside the bar magnet the field is in one direction while outside the field is in opposite direction.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 13, 2007 #2


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    Gold Member

    The field lines travel in closed loops i.e loops don't start or stop at any point, or even cross paths. This would explain why its south to north inside the bar magnet.
    For current flowing in a conductor, the field lines are circles around the conductor. They dont start from north to south for example.
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