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Electro Magnets Answered

If an electro magnet is suspending something in an vacuum environment, will it act as a medium? (Will sound waves be able to pass through the magnetic field?) Thanks


I 'think' if the mechanism operated in a vacuum, given time, mechanical failure would occur before sound was generated or affected in any manner. All by definition that sound waves cannot propagate in a vacuum. Kinda puts a damper on the reality of about every sci-fi movie ever made.


10 years ago

No. There will be no sound whatsoever because there's no air for the speaker to produce sound in. The speaker diaphragm will be oscillating, but with no effect on it's surroundings.

However, there will be an interaction between the magnetic field produced by the speaker coil and the electromagnet holding the assembly in place. If a sinusoidal voltage is applied to the speaker coil, it will be alternately attracted and repelled by the constant magnetic field of the electromagnet. It might be possible to observe a slight up and down motion of the speaker, but this oscillation will be very small. Again, with no air molecules to compress and expand, any oscillations will not be audible.

There's a classic lecture demonstration where a siren and a light are placed in a bell jar that's connected to a vacuum pump. At atmosphere, you can see the light and hear the siren. But as the air is removed, the light intensity does not change while the siren gets quieter until it's completely silent.

Thanks, that's what I thought, but Mr. Nacho though differently =[]

. I don't think you worded the question very well. The setup that we discussed was an air-filled chamber suspended by a magnetic field, in a vacuum. The question was whether or not noise produced in the chamber would be detectable at the coil as a vibration. Ie, would the mag field "conduct" sound?

You're going to be very careful with your definitions. By definition, a magnetic field does NOT "conduct" sound, because sound by definition is mechanical vibrations in matter. However, you might be able to say that the apparatus TRANSMITS sound by first converting it to variations of a magnetic field. You might as well say that a radio signal "conducts" sound through space when NASA talks to their astronauts...

. That's why I put conduct in quotes. Maybe transfer would be a better word. . What I am trying to get at is: if a room is held up by a mag field (generated by a coil (or whatever) attached to the ground), will changing forces/vibrations applied to the platform be transmitted to the ground. Specifically, could one put a transducer between the coil and ground and reproduce the sound made in the room. . The vacuum was just to isolate the room. . I say yes (whether you have an iron rod, an air mattress, or a mag field, the forces/vibrations will reach the ground) and W'burg says no.

The other part to remember is that the field will be surrounded in the magnets, to keep it it in the same place.

. My _theory_ is that the mag field will act like a very stiff spring and conduct vibration.