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Q & A: waves and fields

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Most recent answer: 06/25/2010
Q:
What is the difference between a magnetic field and a magnetic wave?
- Michael French
Napavine, WA
A:
A wave is just a field pattern which propagates from one place to another. Electromagnetic fields obey Maxwell's equations, which include propagating wave solutions. These propagating solutions always have an electric component as well as a magnetic one.

Mike W,

(published on 05/29/2010)

Follow-Up #1: To propagate or not to propagate?

Q:
why do some fields propagate, like one coming from a radio antena, and others don't, like a permanant magnet?
- Michael French
napavine
A:
Interesting question.  The propagating radiation fields from a radio antenna arise from the fact that electric charges are oscillating within the antenna structure. These back and forth oscillations imply acceleration of the electric charges.  Accelerating charges, according to Maxwell, initiate radiation fields.  On the other hand a permanent magnet at rest on a table just sits there, it has a static field with no oscillations at all.  However if you would shake the magnet very rapidly back and forth there would be a radiation field, although weak.

LeeH

If the electric and magnetic fields have components at right angles to each other, then there will  be a flow of energy via the field. That's at least a necessary part of the propagation. MW

(published on 06/25/2010)

Follow-up on this answer.