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 Applying Maxwell's Law
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By: Anonymous: The Student () on Sunday, February 19 2012 @ 09:17 AM PST (Read 1544 times)  
Anonymous: The Student

I would like to ask if it is possible to apply Maxwell's law in the design of a variable-frequency electromagnetic wave emitter. Put simply, I would like to know if it is possible to design, using the concept I am about to put forward, a machine that can emit radio waves, micro waves, or any frequency of wave you want within the limits of the components of the circuit.
First of all, I am sure that someone has already done this, but I just couldn't google it up. Secondly, microwave generation is usually performed using an electron beam fired into a magnetic field, not using this.
Imagine a pair of electric plates with opposite charges facing each other. Imagine also a pair of wire coils which will serve as sources of a changing magnetic field at right angles to the pair or electric plates. Maxwell showed that electromagnetic waves (Light, radio waves, etc)
are composed of oscillating magnetic and electric components that are self sustaining and can move through a vacuum. Now, we run an alternating current through the plates and wire coils such that the space between them will have changing electric and magnetic fields at right angles to each other. The current flows such that the polarity of the electric fields and the magnetic poles are reversed at the same instant, thus ensuring that the generated electromagnetic wave will move in one direction only. Theoretically, this should produce an electromagnetic wave. If we increase the frequency of the alternating current, the frequency of the generated wave should increase too.

I'm not too sure if this will work. I wonder if I'm interpreting Maxwell's law wrongly, because after all, microwaves are generated by passing electrons, through a magnetic field, and not using the method I proposed, which does not make use of an electron beam. Any feedback, correction, or critique of my proposal is much appreciated.
(By the way, I'm just doing my first year in electronic and computer engineering, in university, so try to keep any technicalities to a minimum. Thanks.)

By: Ugi (offline) on Tuesday, February 21 2012 @ 07:27 AM PST  

What you have described is essentially a radio transmitter - except you only need one half of your setup.

The thing is, an oscillating electric field will generate a corresponding magnetic field etc. When you use an areal to transmit radio waves, you apply an alternating current of the correct frequency, which generates an electric field, which propagates a corresponding magnetic field, and suddenly you have EM radiation.

The problem is that you run into a few practical difficulties when you get much beyond microwaves - your microwave oven uses a magnetron but your wireless router uses microwaves from an areal just like a radio transmitter, only if you read the back it will say something like 2.4 or maybe 5 GHz. So to drive that you need a 5 GHz circuit.

5 GHz is entirely doable but still damned fast and you need to miniaturise everything and kill as much capacitance in the system as you can etc. Now try doing that with visable light, which you need to drive at (thank you Wikepedia) a frequency range of about 405 THz to 790 THz or UV at 750 THz to 30 PHz, or X-rays at 30 petahertz to 30 exahertz.... I'm running out of prefixes here but you get the idea. It's a great and simple way to do it if you can only make it work!

Here's a link to a 1 THz oscillator that I found by Googling. It needs cooling to -150'C to get above 20 uW at 1.7 THz and in 2005 was worth an academic paper joint-authored by the California Jet-Propulsion Laboratory and the University of Paris. And they are still somewhere in the far infra-red. That makes it a pretty tough way to light your house!

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By: Anonymous: The Student () on Wednesday, February 22 2012 @ 06:33 AM PST  
Anonymous: The Student

Dear Ugi,
Thanks for your reply. It was really informative. Um, I would also like to know if the set-up I proposed could be used to send the E.M waves in just one direction, kind of like polarized light. Also, I would like to know if it would be possible to reach strong intensities of microwaves with this kind of set-up (By lining up many of these units in one straight line and giving them each their own power source). Finally, I am aware that it is just another radio transmitter, but I would also like to know if there would be any difference in its output, as the electric plates are arranged like capacitors and no current flows in them. Essentially, I would like to know if the electric field alone together with a magnetic field oscillating repetitively would produce unidirectional radio or micro waves which are more focused and have a greater intensity than a common radio transmitter.
Your feedback is much appreciated.


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