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Name: Dana
Status: student
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Question:
What causes magnets to be bipolar? Why, for instance, not tripolar? Why is magnetic north always north and magnetic south always south? (Except during reversals.) I am learning about electromagnetism and particularly domain theory in school, and I could not find a satisfactory answer on the web or in my textbooks.



Replies:
Dana,

Magnetic field is bipolar because a magnetic field at one position can have only one direction. There is not uniform magnetic charge, so a magnetic field cannot just point outward or inward like an electric field. A magnetic field forms continuous loops. At any point on the loop, it can have only one direction, appearing to point from one direction to another.

A magnet tends to align itself with the magnetic field around it. North and South for magnets are "north-seeking" and "south-seeking" when stated completely. The north end of the Earth is a south-seeking magnetic pole. The south end of the Earth is a north-seeking magnetic pole. Opposites attract for magnets. The north-seeking pole of a magnet is drawn toward the south-seeking pole of the Earth (i.e. the north end). If the magnetic field of the Earth should reverse, the south end would become the south-seeking pole.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College


Neither classical electromagnetic theory, nor quantum mechanical electromagnetic theory excludes the possibility of the existence of a magnetic "monopole" analogous to the electron. However, attempts to find the "beast" to date have not been successful -- but not for lack of effort.

The discovery of a magnetic monopole is a Nobel Prize waiting to be won!!

The "reason" you do not find this discussed in high school texts (or many introductory college texts either) is that the "reason" involves vector algebra and calculus -- math that has not been taught at those levels, at least not yet.

Vince Calder



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