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Force on moving charge in ELECTRIC field

  1. Nov 26, 2014 #1
    1. The problem statement, all variables and given/known data
    The diagram shows the path of a charged particle through a uniform electric field, having vertical
    field lines.

    (the iamge has been attached)

    What could give a path of this shape?
    A a positive charge travelling left to right in a field directed downwards
    B a positive charge travelling right to left in a field directed downwards
    C a negative charge travelling right to left in a field directed upwards
    D a negative charge travelling left to right in a field directed downwards

    2. Relevant equations


    3. The attempt at a solution
    Ans is D. but i can't understand. it's an electric field. flemming rules don't apply. why is D correct. and the other wrong. shouldn't a -ve charge just move vertically up??
     

    Attached Files:

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  2. jcsd
  3. Nov 26, 2014 #2

    andrevdh

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    I think you should assume that the particle enters the
    region in which the field exists with a certain speed.
     
  4. Nov 26, 2014 #3
    even with this assumption, won't an electron moved up in a field directed downward???
     
  5. Nov 26, 2014 #4

    andrevdh

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    The charge enters the field moving downwards at an angle and gradually turns upwards.
    The field indicates the direction of the force on positive charge, so negative charge experiences
    an upwards force. This means that its direction of motion is turned upwards while it is moving along.
     
  6. Nov 26, 2014 #5
    thanks. so, we had to assume the charge enters at an angle.
    i've been thinking for a long time on the question, but never assumed this
     
  7. Nov 26, 2014 #6

    andrevdh

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    Yes the path/curve bends downwards a bit
    where it enters the field.
     
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