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Unformatted text preview: EE3321 Electomagnetic Field Theory Lesson 6 1. Magnetic Field A magnetic field is a vector field that exerts a magnetic force on moving electric charges and on magnetic dipoles (such as permanent magnets). When placed in a magnetic field, magnetic dipoles tend to align their axes to be parallel with the magnetic field, as can be seen when iron filings are in the presence of a magnet. In the figure above, the high permeability of individual iron filings causes the magnetic field to be larger at the ends of the filings. This causes individual filings to attract each other, forming long clusters that trace out the appearance of lines. Exercise : Observe the magentic field of a magnetic dipole with the experimental kit provided. The direction of the magnetic field near the poles of a magnet is revealed by placing compasses nearby. As seen below, the magnetic field points towards a magnet's south pole and away from its north pole. Exercise: Identify the magnetic poles of the Earth. Force between two magnetic poles. The force between two magnetic poles is given by: where • q m 1 and q m 2 are the magnitudes of magnetic poles (Ampere meter) • μ is the permeability of the intervening medium (Newton per Ampere squared) • r is the separation (meter) Force between two bar magnets. Suppose that two bar magnets of equal length L are placed end-to-end along the x axis. The spacing between the two magnets is x as illustrated below....
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- Fall '08
- Magnetic Field