1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Help are any of these even correct?

  1. Jun 6, 2007 #1
    I've done some background research but can't find a definite answer to this question. At first i suspected the answer to be A but everyone seems to have their own thoughts about it:

    The reason the north pole of a bar magnet (which is free to rotate) points north is because:

    a. the south geographic pole of the earth is the earth's magnetic north pole

    b. the south geographic pole of the earth is the earth's magnetic south pole

    c. there is a net accumulation of negative charge at the earth's south geographic pole

    d. there is a net accumulation of positive magnetic charge at the earth's north geographic pole

    e. the north geographic pole of the earth is the earth's magnetic north pole

    i'm pretty sure c and d can be eliminated but that still doesn't make the question much easier to answer
     
  2. jcsd
  3. Jun 6, 2007 #2

    andrevdh

    User Avatar
    Homework Helper

    They are all wrong.

    The geographic and magnetic poles do not coincide.

    A magnet aligns itself with the magnetic field lines.

    The magnetic field lines stretches from the north pole towards the south pole of a magnet. This means that the noth pole of a magnet will point towards the south pole of another magnet (unlike poles attrack each other). The N point of a compass is therefore actually the south pole of a magnet.
     
    Last edited: Jun 6, 2007
  4. Jun 6, 2007 #3
    I'm not quite sure that explanation is quite correct.

    This explanation may work better for you. When the phenomenon was first discovered, it was noticed that one end of a bar magnet would orient itself toward earth's North Pole. This end of the bar magnet was called the north-seeking pole, or shortened, N. So, your bar magnet has two poles: N and S. The S is really the "south seeking pole."

    Now, if you think about magnets merely as having "north and south poles", then for the north pole of a magnet to be attracted to Earth's north pole, then earth's north pole is actually a magnetic south pole. This really isn't a problem though, because it means "south seeking pole" - which of course, opposite poles of a magnet are attracted to each other, thus regardless of what we call Santa Claus country, it's going to be attracted to penguin-land.

    A compass needle points in the direction of the magnetic field. Lines of flux are drawn from North to South. So, it will orient itself pointing to the "S" on a bar magnet. In order for it to do this, the tip of the compass needle (on the side it points to) must be a "N-pole". Thus, a compass points toward "S", and earth's North pole is a magnetic S-pole.
     
    Last edited: Jun 6, 2007
  5. Jun 6, 2007 #4
    Oh, and for what it's worth, choices b and e are essentially the same. You are correct that it's answer A, although andrevdh is correct in pointing out that the geographic north pole and magnetic north pole are not in the same place.

    I should emphasize though, it's called "The Magnetic North Pole" - it IS the North Pole. And, of course, as a north pole, it's going to be south-seeking. Bar magnets are labeled by which pole they're seeking, so if you label the earth as a bar magnet (and in reality, the source of the magnetic field is NOT bar shaped; that's another discussion though) then you need to label that thing up in the Arctic Ocean a "south-seeking pole" or S. But, again, it IS the Magnetic North Pole.

    And, as andrevdh noted, it's not located at the geographic north pole. Plus, it moves around a bit, varying daily, and changing location by about 10 to 50 kilometers each year. The changing location of the magnetic north pole hasn't been missed by the media. They love to sensationalize on such things; there were several such stories a few months ago.

    Here is a site that seems to have some quality info, if you need more:
    http://gsc.nrcan.gc.ca/geomag/nmp/northpole_e.php
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?