Transcript Magnetism & Electromagnetism

Electrical/Electronics
Magnetism & Electromagnetism
Volume 2 of 5
Grade 11
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What is Magnetism?
 Magnetism is the force of attraction or
repulsion in a material. Certain materials such
as iron, steel, nickel, or magnetite exhibit this
force while most other materials do not.
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What are Magnets?
 A magnet is a material or object that
produces a magnetic field. This magnetic field
is invisible but is responsible for the most
notable property of a magnet: a force that
pulls on other ferromagnetic materials and
attracts or repels other magnets.
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Magnetic Field
 A magnetic field can be represented by lines
of induction or flux lines. These lines are
invisible and are produced by magnetized
material or by electrical currents. Magnetic
fields are electrical in nature, and the
magnetic field caused by a long straight line
of current is simulated in Figure 1.
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Magnetic Fields
Fig.1
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Magnetic Materials
 Ferromagnetic - metals that are easily
magnetized; iron, nickel, cobalt,
manganese
 Paramagnetic - metals that can be
magnetized but not as easily as
ferromagnetic; platinum, titanium, and
chromium
 Diamagnetic - metal or non-metallic
materials that cannot be magnetized;
copper, brass, and antimony
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Electromagnetism
 This is the changing magnetic field produces
an electric field (this is the phenomenon of
electromagnetic induction, the basis of
operation for electrical generators, induction
motors, and transformers). Similarly, a
changing electric field generates a magnetic
field
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Electromagnetism Creation
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Gauss's Law for magnetism
 It states that the magnetic field B has
divergence equal to zero, in other words, that
it is a solenoid vector field. It is equivalent to
the statement that magnetic monopoles do
not exist. Rather than "magnetic charges", the
basic entity for magnetism is the magnetic
dipole. (Of course, if monopoles were ever
found, the law would have to be modified, as
elaborated below.)
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Coulomb's Law of Magnetism
 The magnitude of the electrostatic force
between two point electric charges is directly
proportional to the product of the magnitudes
of each of the charges and inversely
proportional to the square of the total
distance between the two charges.
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Reference
For further reading you can check out the
following websites:
http://en.wikipedia.org/wiki/Coulomb%27s_law
http://science.howstuffworks.com/magnet.htm
http://www.coolmagnetman.com/magindex.htm
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