Electric charge in motion
المؤلف:
Stan Gibilisco
المصدر:
Teach Yourself Electricity and Electronics
الجزء والصفحة:
136
18-4-2021
2139
Electric charge in motion
Whenever the atoms in a ferromagnetic material are aligned, a magnetic field exists. A magnetic field can also be caused by the motion of electric charge carriers, either in a wire or in free space.
The magnetic field around a permanent magnet arises from the same cause as the field around a wire that carries an electric current. The responsible factor in either case is the motion of electrically charged particles. In a wire, the electrons move along the conductor, being passed from atom to atom. In a permanent magnet, the movement of orbiting electrons occurs in such a manner that a sort of current is produced just by the way they move within individual atoms.
Magnetic fields can be produced by the motion of charged particles through space. The sun is constantly ejecting protons and helium nuclei. These particles carry a positive electric charge. Because of this, they have magnetic fields. When these fields interact with the geomagnetic field, the particles are forced to change direction. Charged particles from the sun are accelerated toward the geomagnetic poles. If there is a solar flare, the sun ejects far more charged particles than normal. When these arrive at the geomagnetic poles, the result can actually disrupt the geomagnetic field. Then there is a geomagnetic storm. This causes changes in the earth’s ionosphere, affecting long-distance radio communications at certain frequencies. If the fluctuations are intense enough, even wire communications and electric power transmission can be interfered with. Microwave transmissions are generally immune to the effects of a geomagnetic storm, although the wire links can be affected. Aurora (northern or southern lights) are frequently observed at night during these events.
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