For this exercise we will be mapping the magnetic fields produced by a bar magne

Question

For this exercise we will be mapping the magnetic fields produced by a bar magnet combined with the earth's magnetic fields. Fields are vector quantity so the resultant magnetic field add up in a vector sense. Magnetic fields are produced by moving charges or electric currents. For example, if you pass a direct current through a wire you can detect the presence of magnetic fields around the wire by using some iron filings or a small compass. In bar magnets there exists magnetic dipoles at the atomic level that are responsible for the presence of the magnetic field. The earth's magnetic fields are the result of the earth molten core which is under constant rotation. The rotation and iron in the molten core acts like a giant current loop. The magnetic south pole of the earth's magnetic fields is near the geographic north pole. The Figure below shows the magnetic fields from a bar magnet. Each of the red arrows represents the direction and magnitude (length of the arrow) of the magnetic field at that point. In addition there is a constant and uniform earth's magnetic field and this is represented by the green arrow. Only one green arrow is drawn, however bear in mind the earth's field is constant throughout the Figure. Your task is to work out the direction of the resultant magnetic field at the different points. Use the compass rose as your direction. Choose the direction that is closest to one of the directions. (Note: For the lab, the direction at each location is determined by using a small compass.)

The resultant magnetic field at G is along ?
• The resultant magnetic field at M is along ?
• The resultant magnetic field at R is along ?
• The resultant magnetic field at L is along ?
• The resultant magnetic field at Q is along ?
• The resultant magnetic field at O is along ?

Answers can be N NE E SE S SW W NW and no dir.

There are two points where the earth's magnetic field cancels the bar magnetic fields. Locate the two points and enter their letters below. For the lab, at the zero field locations, a compass needle does not have any preference direction

Explanation / Answer

   The resultant magnetic field at G is along E
• The resultant magnetic field at M is along W
• The resultant magnetic field at R is along S
• The resultant magnetic field at L is along E
• The resultant magnetic field at Q is along no dir
• The resultant magnetic field at O is along W

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