I have a question that I am trying to figure out:

  1. Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current toward you, and the wire on your left carries current away from you. From your point of view, the magnetic field at the point exactly midway between the two wires

a. points upward.

b. points downward.

c. points toward you.

d. points away from you.

e. is zero.

I am using the right hand rule and just really confusing myself. It's easy for the current that is facing me. I point my thumb in my direction and see that my fingers wrap in a direction "down." However, when I point my thumb away from me, if my palm is facing up, then my fingers will wrap up, but if my palm is facing down, then my fingers will wrap down. I don't understand which way is the correct way to hold my hand, whether my palm should always be up or down. I know there are other "right hand rules" but this is the one I've been using until now and I have a test in a few hours so I really can't learn a "new" one, so could somebody clarify my confusion for me?


1 Answer 1


Note that a current carrying wire produces a circular magnetic field that's why it doesn't matter how you hold your hand ie how you rotate your hand around your arm as long as your thumb shows the direction of the current.

Edit after comments:

See the illustration I've added below. Now use your hand in the way that you've learned and convince yourself that what I've drawn below is correct.

enter image description here

  • $\begingroup$ Right, but for my particular question, the correct answer is that the magnetic field points "downward." That IS confusing to me since I know they go in a circular path, but I guess what it means by "downward" is that it is moving counterclockwise. If my thumb points away from me and I hold it one way, it gives the impression that the current is going clockwise (down), and if I hold it the other way, it looks like the current is going counterclockwise (up). That is where my confusion is @gonenc $\endgroup$ Commented Mar 30, 2015 at 7:34
  • $\begingroup$ I think what you say is correct ie you cannot really say that the magnetic field points downward. In my opinion that utterly doesn't make any sense. Check in your question if they are asking the magnetic field on a particular point. Other than that I would always say eg clockwise or counter clockwise looking from below or in the direction of the current. Of course the best way is to give the magnetic field vector itself :) $\endgroup$
    – Gonenc
    Commented Mar 30, 2015 at 7:37
  • $\begingroup$ yeah, it asks at the point "exactly midway between the two wires" @gonenc $\endgroup$ Commented Mar 30, 2015 at 7:40
  • $\begingroup$ Then there is one unique answer, position your hand such that your thumb shows in the direction of the current and your fingers are sticking out between the two wires. This would be really easy to demonstrate if I could show you how to position your hands! $\endgroup$
    – Gonenc
    Commented Mar 30, 2015 at 7:43
  • $\begingroup$ I don't know what you mean by "sticking out between the two wires" ...I can do that and still am not sure whehter the magnetic field is going up and down $\endgroup$ Commented Mar 30, 2015 at 8:01

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