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"In physics, resonance is the tendency of a system to oscillate at maximum amplitude at a certain frequency. This frequency is known as the system's resonance frequency. When damping is small, the resonance frequency is approximately equal to the natural frequency of the system, which is the frequency of free vibrations." ( from Wikipedia, 8/8/2007)
With this Instructable I'll show you a simple rig that can be used to experiment with electromechanical resonance.
With this Instructable I'll show you a simple rig that can be used to experiment with electromechanical resonance.
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Of all the aspects of physics we can investigate with simple household items, magnetism is the most exciting to me. Although I'm sort of grown up I still love pushing magnets one against the other just to feel the magic repulsive force.
Repulsive force for some reason is more entertaining than the attractive one. In this field, I mean.
We know that when a current flows through a metallic wire a magnetic field is generated; that's what electric motor are based upon.
The wire can be wound in the shape of a bobbing to make the field stronger and a metallic core can increase the strength of the field. The equations linking number of turns, coil diameter and current can be found here (http://en.wikipedia.org/wiki/Electromagnet) but it is not strictly necessary to understand the underlying principles.
A direct current, the one from batteries, generates a constant magnetic field. The direction of the magnetic field with respect to current is established conventionally by the so-called right hand rule : with reference to the picture, grabbing the coil with our right hand with the thumb pointing the same direction of the current, the magnetic field will have the direction of the other four fingers.
The direction of current is, again, conventionally fixed going from the + pole of the battery through the wire to the - pole.
Alternating current (a.c.), the one that comes out a regular wall socket, will have the same effect except that the intensity of the current flowing through the coil wire cyclically rises to a maximum then decreases to a minimum in the opposite direction passing through a zero current level. As a consequence, a.c. powering a coil generates an alternating magnetic field that cyclically rises to a maximum value then decreases to a minimum passing through a zero field value.
It is important to note that the field does not rotate in any direction. Simply rises and falls in intensity then reverse its verse and rises again.
Repulsive force for some reason is more entertaining than the attractive one. In this field, I mean.
We know that when a current flows through a metallic wire a magnetic field is generated; that's what electric motor are based upon.
The wire can be wound in the shape of a bobbing to make the field stronger and a metallic core can increase the strength of the field. The equations linking number of turns, coil diameter and current can be found here (http://en.wikipedia.org/wiki/Electromagnet) but it is not strictly necessary to understand the underlying principles.
A direct current, the one from batteries, generates a constant magnetic field. The direction of the magnetic field with respect to current is established conventionally by the so-called right hand rule : with reference to the picture, grabbing the coil with our right hand with the thumb pointing the same direction of the current, the magnetic field will have the direction of the other four fingers.
The direction of current is, again, conventionally fixed going from the + pole of the battery through the wire to the - pole.
Alternating current (a.c.), the one that comes out a regular wall socket, will have the same effect except that the intensity of the current flowing through the coil wire cyclically rises to a maximum then decreases to a minimum in the opposite direction passing through a zero current level. As a consequence, a.c. powering a coil generates an alternating magnetic field that cyclically rises to a maximum value then decreases to a minimum passing through a zero field value.
It is important to note that the field does not rotate in any direction. Simply rises and falls in intensity then reverse its verse and rises again.
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Switching supplies are usually labelled as such.
-Mike
The AC in 'heavy' iron transformer based adapters can be taken right at the wires coming out the transformer (should look very similar to this one http://en.wikipedia.org/wiki/Image:Transformer.filament.agr.jpg ) before they go to the rectifier. The rectifier could have the shape of a black tiny cylinder or box or could be made with one, two or four diodes.
<disclaimer>
Be careful and stay away from the primary high voltage.
Always make connections with the adapter off line.
Always seek help from expert friends.
</disclaimer>
If you need more directions just write.
Ciao e divertiti. (have fun)
The same can be done with a DC current flow equal to the maximum peak to peak current of the amp. Ohms law can be used to determine this.
-Mike
http://mpc-hc.sourceforge.net/download-media-player-classic-hc.html
and get all the codec's you'll ever need:
http://sourceforge.net/projects/ffdshow/
-Mike
Thanks for this instructable. I am interested in the tuning you mentioned. I am working on a project using electromagnetic force to vibrate objects for musical purposes. what is the tuner? might i be able to use it to excite different resonant frequencies in a given form ..say a metal bin? i am new to this art form ..having spent some years playing with ceramic material i am now in the middle of metal things and vibrations are forever calling me! any thoughts on how i could play the different partials of an objects with eltromagnets? smile. thanks
In case of a large bin you may need to to tune the oscillator frequency as the bin is home to a large number of natural frequencies. In case you need a sinusoidal oscillator, a large strong coil with an iron core, a power audio amplifier suitable to drive the coil and a large magnet to be placed somewhere around the bin or at its bottom. Connect the coil to the amplifier (do not connect any speaker - expect that you might destroy your amplifier, so you'd better not use your home Harman Kardon HiHiFi amplifier).
Turn on the amplifier at a low level first and place the coil near the magnet on the bin then start playing with the frequency of the oscillator to excite the partials of the bin. When you hear something interesting, pull up the volume and enjoy.
Again, be prepared to damage your amplifier, wear safety goggles as the magnet might be ejected.
Ciao
A
If it's a tube amp, the opposite is true. You must NEVER operate a tube power amp with no load. It will generate high voltages that will arc the power tubes and output transformer. Tube power amps will withstand output short circuits that would quickly toast a solid state power amp.
-Mike
I was thinking 'bout creating a feedback with a microphone on the bell (screened from the speaker) : together with a phase-shifting network one should be able to force the bell into a partial.
This thing is calling me...Argh ! No ! No, have to finish the MIDI thing first !
Cheers !
Alex
So blame it on math.
-Mike
in short, you're right. lol
-Cheers
See also http://en.wikipedia.org/wiki/Electromagnet
http://www.physlink.com/education/askexperts/ae695.cfm
My experience with perpetual motion is that it's impossible unless it somehow involves women. (Ducking sudden appearance of hurled frying pans and irons).
-Anonymouse