PHYS 142 Lecture Notes - Lecture 21: Vacuum Permeability, Cross Product
29 Apr 2015
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Phys 142: electromagnetism and optics - lecture 21: magnetism part 1. Magnetism is not the same as electricity. All magnets have two poles, called north and south poles. Two like poles exert repulsive forces on each other; two opposite poles attract. The poles of a bar magnet can be identified by using it as a compass. Materials that are attracted to a magnet are called magnetic materials. The most common rotate to point approximately north. magnetic material is iron. A current carrying wire creates a magnetic field around that wire. Because compass needles align with the magnetic field, the magnetic field at each point must be tangent to a circle around the wire. In other words, the direction of the magnetic field is determined by the right hand rule. The field is weaker (shorter vectors) at greater distances from the wire. Magnetic field lines are imaginary lines drawn through a region of space so that:
