MAGNETIC FIELD & MAGNETIC FORCES SOURCES OF MAGNETIC FIELD
KEY TERMS: permanent magnet, magnetic monopole, Tesla, Gauss, magnetic field line, magnetic flux, Weber,mass spectrometer, magnetic dipole moment or magnetic moment, solenoid, Hall effect.
There are no individual magnetic poles (or magnetic charges). Electric charges can be separated, but magnetic poles always come in pairs - one north and one south.
Opposite poles (N and S) attract and like poles (N and N,or S and S) repel.
These bar magnets will remain "permanent" until something happens to eliminate the alignment of atomic magnetsin the bar of iron, nickel, or cobalt.
Fig. 1 Bar magnets (permanent magnets)
The Earth's magnetic field appears to come from a giant bar magnet, but with its south pole located up near the Earth's north pole (near Canada).
The magnetic field lines come out of the Earth near Antarctica and enter near Canada.
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Fig. 2 Earth's magnetic field
The connection between electric current and magnetic field was first observed
when the presence of a current in a wire near a magnetic compass affected
the direction of the compass needle. We now know that current gives rise to magnetic fields, just as electric charge gave rise to electric fields.
Fig. 3 Compass near a current-carrying wire
The Earth's surface and its inhabitants are protected from dangerous cosmic radiation (energetic protons) from the Sun by the Earth's magnetic field.
Using the right-hand rule one can see that positively charged particles coming from the Sun will be deflected in an easterly direction.
Fig. 4 Van Allen radiation belts around the Earth
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