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Does the magnetic north pole of a magnetic compass change direction through Earths hemispheres?

From my understanding, the Earth is similar to a permanent bar magnet in that it has 2 poles, North and South, where it's South pole is positioned geographically north. I know it's field direction and magnitude changes with time but lets assume it is still in this orientation and constant.

Let's say the compass is spherical so that the needle can point both vertically and horizontally.

In the Northern Hemisphere would the North Pole of this compass point towards the geographical north pole i.e. be oriented vertically with the north pole on top pointing towards the magnetic south pole of the earth.

In the Southern Hemisphere would the North Pole of this compass still point towards the geographical north pole and maintain its same orientation as described in the Northern Hemisphere case? I thought it would maintain this orientation as it would be repelled by the earths magnetic north pole which is geographically south.

Thanks in advance.

Update:

Thanks for your response Gary, that's exactly what I was looking for.

However, I don't see how the compass would point upwards in the geographical southern hemisphere, in the diagram it appears that it would point in a downwards direction throughout the whole planet, except for the equator where it would point upwards. The red tip showing the direction of the north pole of the magnet, never seems to point up apart from the equator. I may be misinterpreting the diagram though.

Update 2:

Ok, I think I understand this concept, but there is a certain question which I still don't understand:

There is a diagram of a bar magnet oriented diagonally showing it's N and S poles which is suspended at its midpoint by a light string so it can rotate in the x-y plane. There are several multiple choice alternatives but there are 2 of which both sound true to me but there can be only one answer.

The magnet is oriented this way:

N

S

The alternatives are:

A. The magnet is in the southern hemisphere and its N end is pointing towards the geographical north pole.

B. The magnet is in the northern hemisphere and its N end is pointing towards the geographical north pole.

How do I tell which hemisphere? Inside the earth, the magnet will always be oriented with N pointing upwards, so how can I eliminate?

Update 3:

N is further to the right than S if the diagonal didn't show up properly.

2 Answers

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  • ?
    Lv 6
    10 years ago
    Favorite Answer

    The easiest way to see the answer to your question is to go to a diagram of the earth's magnetic field that includes the field directional arrows. There is one at ref 1. The arrows show the direction in which magnetic north of a compass will point.

    The tricky thing about the terminology is summed up in the first sentence of the article:

    "Earth's magnetic field (and the surface magnetic field) is approximately a magnetic dipole, with the magnetic field South pole near the Earth's geographic north pole (see Magnetic North Pole) and the other magnetic field N pole near the Earth's geographic south pole (see Magnetic South Pole)."

    In other words, the magnetic field South pole (labeled S in the diagram) IS the Magnetic North Pole, which is located near the geographic North Pole! Once you get used to this, you can use the diagram as follows:

    You can see that, at the geographic South Pole, the spherical compass will point upwards--that is, outwards from the surface of the earth and perpendicular to it.

    At the equator it will point towards magnetic North Pole, and tangent to the surface of the earth.

    At magnetic North Pole (near geographic North Pole) it will point down towards the earth's center, perpendicular to the surface.

    .

  • 10 years ago

    Given that you are asking for both the vertical and horizontal aspects of the needle then first we look at the horizontal. The North seeking end of the magnet points to the appropriate pole of the earth which is a little away from the North pole itself.

    For the vertical angles remember that the magnet will orient itself along a magnetic field line.

    It doesn't point directly to a pole at all.

    If you sketch the field lines around a bar magnet you can see that from the pole they are almost perpendicular to the surface. At the equator the lines are parallel to the surface.

    Close to either pole but not at it then there is substantial declination. The magnet dips substantially toward the nearer pole.

    Translated At the south pole ( north magnetic pole) the north seeking end of the magnet will point almost vertically up from the earth and strangely, away from the north pole.

    At a latitude of around 70 degrees the North seeking end of the magnet would point north of course but it would point above the horizon by quite a bit.

    As you get nearer to the equator the magnet would be flat and level.

    Then getting closer to the North pole the South seeking end would be the one that points above the horizon.

    Until finally at the north pole then the south seeking end would point straight up in the air.

    All of the above can be easily estimated by simply drawing a series of concentric circles on a piece of paper, then putting a bar magnet on that paper.

    Finally sprinkling iron filings on top to display the direction of field lines.

    The angles of those field lines from the circle shows ( approximately) the vertical angle of the magnetic field of the earth at similar points.

    Of course in practice there are variations caused by the amount of iron in the crust at different points but these are local variations on a more general theme.

    To extend your slightly more simple view. Near the North pole ( south magnetic pole) the north end is attracted so it is pulled downwards.

    Near the south pole ( north magnetic pole) the north end is repelled so it is pushed upwards.

    I think this is the question that you are asking.

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