I'm dealing with a problem here. Today my professor asked us a question :

How should a metallic wire move in Earth's magnetic field such that she gets maximum potential difference in it's ends:

a) Horizontally b) Vertically c) Normal in the magnetic field lines

Can anyone help me with this question?

Thank you !

  • $\begingroup$ A conducting wire, surely? What have you tried? $\endgroup$
    – rob
    Commented May 5, 2014 at 20:05
  • $\begingroup$ Oh sorry. Now I corrected the question. Well I think it's option c but I'm not quite shure. $\endgroup$
    – Student
    Commented May 5, 2014 at 20:07
  • $\begingroup$ Why do you think so? Why are you not sure? Show us what you have tried. $\endgroup$
    – rob
    Commented May 5, 2014 at 20:08
  • $\begingroup$ I thought so because I think when the wire moves normal she hits a big number of magnetic field lines(the maximum that she can hit). $\endgroup$
    – Student
    Commented May 5, 2014 at 20:15

1 Answer 1


This question is pretty easily solved with an application of the Right Hand Rule. If your thumb points in the direction of motion, and your index finger points in the direction of the magnetic field, then the other finger point in the direction of the force.

So, the magnetic field of the earth goes (roughly) in the north-south direction. You would want the wire to move in a direction perpendicular to the field lines to maximize the effect from the field. Additionally, you'd want the electrons to be at one end of the wire, at a maximum distance away from the other end. So the wire would lay along your "force" direction finger.


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