Magnetic Poles

A magnetized bar has its power concentrated at two ends, its poles; they are known as its north (N) and
south (S) poles, because if the bar is hung by its middle from a string, its N end tends to point northwards and its S end southwards. The N end will repel the N end of another magnet, S will repel S, but N and S attract each other. The region where this is observed is loosely called a
magnetic field;
But this property
of iron is a very special type of magnetism, almost an accident of nature!

Out in space there is no magnetic iron, yet magnetism is widespread. For instance, sunspots consist of glowing hot gas, yet they are all intensely magnetic. The Earth's own magnetic powers arise deep in its interior, and temperatures there are too high for iron magnets, which lose all their power when heated to a red glow. What goes on in those magnetized regions?

 

It is all related to electricity.


Matter consists of electrically charged particles: each atom consists of light, negative electrons swarming around a positive nucleus. Objects with extra electrons are negatively (-) charged, while those missing some electrons are positively (+) charged. Such charging with "static electricity" may happen sometimes unintentionally! when objects are brushed with cloth or fur on a dry day.


Two parallel currents in the same direction attract each other.
Two parallel currents in opposite directions repel each other.
Here is how this can lead to the notion of magnetic poles.
Bend the wires into circles with constant separation.
Two circular currents in the same direction attract each other.

Two circular currents in opposite directions repel each other.

Replace each circle with a coil of 10, 100 or more turns, carrying the same current the attraction or repulsion increase by an appropriate factor. In fact, each coil acts very much like a magnet with magnetic poles at each end an "electromagnet". Each atom of iron contained a circulating current, turning it into a small magnet, and that in an iron magnet all these atomic magnets were lined up in the same direction, allowing their magnetic forces to add up.

The magnetic property becomes even stronger if a core of iron is placed inside the coils, creating an "electromagnet"; In fact, some of the world's strongest magnets contain no iron, because the added benefit of iron inside an electromagnet has a definite limit, whereas the strength of the magnetic force produced directly by an electric current is only limited by engineering considerations.

 

The Earth's Geomagnetic field and The Body



 

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