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Magnetic Forces. Magnetism & Fields. Magnetism. L aw of magnetism states that like magnetic poles repel and unlike poles attract each other. Magnetic Field.
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Magnetic Forces Magnetism & Fields
Magnetism • Law of magnetism states that like magnetic poles repel and unlike poles attract each other.
Magnetic Field • Magnets exert forces that seem to originate from the magnetic poles, and they can affect another magnetic object even without contact. • The ancient Greeks called this effect “action at a distance.” • Field lines are “lines of force”
Magnetic Field Magnetic field lines have the following properties: • magnetic field lines are continuous loops that never cross • inside the magnet, the magnetic field lines point from the south pole to the north pole • outside the magnet, the magnetic field lines point away from the north pole toward the south pole • the closeness of the lines represents the strength of the magnetic field (the closer the lines are together, the stronger the magnetic field) • • if the field lines are parallel, the magnetic field is uniform
Magnetic Field 1 Tesla = 1 T = 1 N / (A*m)
Domain Theory • A material that is made from a magnetized material and creates a magnetic field is a permanent magnet. • Some materials become magnetized when they are placed in an external magnetic field. These are called ferromagnetic materials, and include iron, nickel, and cobalt.
Domain Theory • The outermost electrons of the atoms of ferromagnetic materials create tiny magnetic fields in each atom. • The magnetic fields of adjacent atoms can align to reinforce each other, forming small regions, or domains, with intense magnetic fields.
Magnetism and Current • Early scientists believed that electricity and magnetism were related, but the link between them eluded scientists until 1820 • Oersted’s principle: When a current moves through a conductor, it creates a magnetic field.
Right Hand Rule • It was shown that when a current flows in a straight conducting wire, the magnetic field forms a circular pattern that is perpendicular to the wire
Solenoid (Coil) • The magnetic field of a solenoid is similar to a bar magnet