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Why field lines are tangent to direction of electric forces

  1. Jun 10, 2010 #1
    can any body tell me why electric field of lines are tangent to direction of electric force

    please be fast need it urgently..........
  2. jcsd
  3. Jun 10, 2010 #2
    They are not "at a tangent". Electric field lines point in the direction of the electric force on a positive charge. They do this by definition.

    Do you mean electric potential lines, perhaps?
  4. Jun 10, 2010 #3


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    Staff: Mentor

    It would be better stated the other way around: the electric field (and electric force) at a point is tangent to the field line that passes through that point. We define the field lines so that they have this property.
  5. Jun 11, 2010 #4
    Maybe this diagram will help
    The 1st shows the electric field around a single positive charge and the 2nd the field in and around a parallel plate capacitor.
    The "field lines" show the direction of the force on a positive charge. The "equipotentials" show places of equal electrical potential.
    The field lines are always at right angles to the equipotentials. This is because the field does no work on a charge moving along an equipotential, meaning the force must be at right angles to its direction of motion.
    Is this what the OP means?
  6. Jun 29, 2010 #5
    Why, oh why did someone feel it necessary to invent those dratted imaginary field lines?

    No-one talks about 'lines of gravitic force'. In fact people would laugh at you for even raising the concept (I can hear them now...)
  7. Jun 29, 2010 #6
    Because they make metal shavings look cool :tongue:
  8. Jun 29, 2010 #7
    Hah! in all the Millenia I've been stuck on this ball of mud I never thought of that!

    You're probably absolutely right.
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