MAGNETIC FORCESMagnetism & 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 LINES
MAGNETIC FIELDMagnetic 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 LINES
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
SOLENOID (COIL)
MAGNETISM
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