Name: Kate M.
I no that by running current though a coil of wire you
create an magnetic field (electromagnet) but what is the principle
behind this? Why does this happen?
Whenever charges are moving they produce a magnetic field as well as the
electric field which they always produce. The magnetic field can be
detected and shown to be different from the electric field because it
produces a force only on moving charges,. You may ask "moving with respect
to what?" Good question. That question played a large role in leading
Einstein to the special theory of relativity.
Those are the basic principles behind magnetism. If you are asking why
those are the principles, I can only say that physics cannot answer such
questions. We can describe magnetism and calculate its effects, but do not
know why the laws of magnetism have exactly that form. It is true, of
course, that almost any change would make the universe unlivable, but
that's a reason for the form the laws have only if you think that the
universe was designed just for mankind. It does rather look that way!
I am not sure I answered your question. Feel free to ask again if you would
like more information.
Best, Dick Plano Professor of Physics emeritus, Rutgers University
Electromagnetism is based on two basic properties of matter: electric
charge produces electric field, motion of electric charge produces magnetic
field. This electric field goes out from or in to the charge, depending on
whether the charge is positive or negative. The magnetic field loops around
the direction of motion. Electric current is many electric charges moving
together through a wire. All the small magnetic fields add together to
produce strong magnetic fields around the wire.
Dr. Ken Mellendorf
Illinois Central College
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Update: June 2012