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Homework Help: Determining the direction of electric field flow and the sign on potential difference

  1. Apr 23, 2012 #1
    1. The problem statement, all variables and given/known data

    A resistor made from a shell with an inner radius r1 and an outer radius r2 hasa conductivity sigma. The current flows radially outward.
    1.What direction does the E field point in.
    2. Is the potential difference V2-V1 positive or negative.

    2. Relevant equations
    None, problem is conceptual.

    3. The attempt at a solution
    As far as I know the electric field flows towards an negative charge and away from a positive charge. I believe that the direction a current flow indicates a flow of positive charge. Thus if a positive charge is flowing outward then the electric field must also be flowing outward in order to move away from the positive charge.

    The potential difference here I believe would also be positive. This is just because in problems that Ive done before when it was postive the electric current was flowing outward. This however, may just be cowincedence. Can someone please explain this concept to me.

    Thank you for your time.
  2. jcsd
  3. Apr 23, 2012 #2


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    Staff: Mentor

    Re: Determining the direction of electric field flow and the sign on potential differ

    Yes, it's basically Ohm's Law. When current flows through a resistance there is a potential drop in the direction of the current flow: E = IR.
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