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Homework Help: Equipotential Lines Question

  1. Feb 2, 2014 #1
    1. The problem statement, all variables and given/known data
    The equipotential curves in a certain region of an equipotential diagram in an xy plane are parallel to the y-axis and are equally spaced. The potential is increasing in the +x direction. Which direction would an electric field vector point in this region?
    2. Relevant equations

    3. The attempt at a solution
    The equipotential lines are vertical, so the electric field lines must be in the x-direction since they run perpendicular to each other. Would they point in the positive x direction since the potential is increasing there? I'm having a hard time picturing what this would look like.
  2. jcsd
  3. Feb 2, 2014 #2
    Try to relate electric field and potential/potential difference- is there any formula by which potential can be written in terms of electric field? Think about it and let me know if you have any question.

    Best of luck!
  4. Feb 2, 2014 #3
    I know that V=∫Edl, but I'm having trouble connecting that to what the equipotential lines would look like.
  5. Feb 2, 2014 #4


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    Suppose the field is created by some distant pair of opposite charges, one in positive x direction and one in the negative. Will the potential be higher towards the positive charge or towards the negative? Which way will the field point?
    No, it's V=-∫Edl. In differential form: E = -dV/dl (or -dV/dx in this context). You're told the potential increases with increasing x, so what is the sign of dV/dx?
  6. Feb 2, 2014 #5
    The potential would be the same at both a positive charge and a negative charge because potential is scalar. The electric field would point towards the negative charge.

    The sign of dV/dx is positive, but when the negative sign is taken into account then E is negative, so the electric field is going in the negative x-direction. Is this correct?
  7. Feb 2, 2014 #6


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    Eh?! Is +3V the same as -3V?
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