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I How is Fleming's left hand rule applied in Hall effect

  1. May 5, 2016 #1
    I've been reading the explanation of Britannica.com about the direction of magnetic force on a moving charge in hall effect.

    "Whether the current is a movement of positive particles, negative particles in the opposite direction, or a mixture of the two, a perpendicular magnetic field displaces the moving electric charges in the same direction sideways at right angles to both the magnetic field and the direction of current flow."
    I don't understand why does a positive and a negative charge feels the magnetic force in the same direction in the hall effect?Because as per the Fleming's left hand rule the moving positive and negative charges should feel the magnetic force in opposite directions.
  2. jcsd
  3. May 5, 2016 #2


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    When a current is flowing, and where both + and - mobile charges are involved, the direction of the force on the negative charges (flowing in one direction) will be the same as the direction of the force on positive charges (flowing in the opposite direction). Minus times minus = plus. Flemmings rule just deals with conventional current (the rule was made long before they found electrons, ions or holes). How that current is carried makes no difference to the result.
  4. May 5, 2016 #3


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    Staff: Mentor

    If the + and - charges are moving in the same direction, the magnetic forces are indeed in opposite directions. However, the + and - charges must move in opposite directions, if the currents they produce are in the same direction. There are two "opposites": opposite charges and opposite directions.
  5. May 6, 2016 #4
    Okay.Thank you all for the help.
    I've understood the direction problem now.
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