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How to Adjust Frequency of EM Wave

  1. Nov 1, 2011 #1
    Alternating current produces EM Wave.

    What determines the frequency(or wave length) of an EM wave related to current or voltage?
     
  2. jcsd
  3. Nov 1, 2011 #2
    If you're talking about low energy AC like in your house, I'm guessing by EM wave you mean the fields near the wires. The frequency of those fields depend on the frequency of the AC, which would be ~60hz in your house. If you're talking about light from AC in a light bulb, that's a different thing.
     
  4. Nov 1, 2011 #3

    davenn

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    its not related to either the current or voltage

    the frequency is determined by the oscillator or other generator

    in a radio transmitter or receiver there are oscillators based for example aroound a crystal oscillating at a wanted frequency
    in the case of your mains power supply to your home its based on the spinning geterator at the power station. 60Hz in some countries of the world, 50Hz in others.

    adjusting the frequency for example in a radio transmitter requires varying the oscillator frequency, this can be done by varying the values of the inductor or capacitor in a tuned circuit. Do some googling on oscillators, tank circuits, local oscillators to start get an idea of what is happening :)

    cheers
    Dave
     
    Last edited: Nov 1, 2011
  5. Nov 1, 2011 #4
    I'm sorry. I think I wasn't clear.

    I didn't ask about the frequency of electricity.

    Electric field generates the Electromagnetic wave and that wave has a frequency.

    Em wave's frequency can be changed and this is why there is an EM spectrum.

    I want to learn what effects the frequency of EM wave?

    For example; 60HZ electricity can generates EM wave, so how can we relate the frequency of electricity with EM wave's frequency? Or is it related?

    What are the parameters that are related with frequency of EM wave?
     
  6. Nov 1, 2011 #5
    The frequency of the wave is determined by the frequency of the AC in the antenna.
    The wavelength depends on the above frequency and the speed of propagation in the medium around the source.
     
  7. Nov 1, 2011 #6
    So 60 hz ac generates 60 hz Em wave. Is that all?

    Is there any formula?
     
  8. Nov 1, 2011 #7
    Pretty much.
     
  9. Nov 2, 2011 #8

    davenn

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    did you actually read my post ?

    The frequency of the AC signal, and therefore any radiated EM wave is determined by the components of the oscillator or generator.
    The formula is in the working out the values of the tuned circuit/speed of rotation of the generator

    That is regardless of if its an audio oscillator or a RF oscillator

    Dave
     
    Last edited: Nov 2, 2011
  10. Nov 2, 2011 #9

    davenn

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    plus a few harmonics ;)

    D
     
  11. Nov 2, 2011 #10

    davenn

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    thats good, cuz electricity doesnt have a frequency as such, But if it is an AC signal it does

    as already said the frequency is changed by changing the values of the oscillator tuned circuit ot the speed of rotation of the generator

    an electric field only produces a radiated EM wave if its oscillating... read my other posts :)
    a 50 or 60Hz mains voltage is only producing a radiated EM wave cuz its oscillating

    cheers
    Dave
     
  12. Feb 16, 2012 #11
    I've been working on this and I think I might have it..

    To Adjust the Freq. of an EM field in a wire:

    get an audio cable, clip it and twist the two live wires together, leaving the braid cable separate

    make a coil which you wish to magnetise

    attach the live part of the audio cable to one end of the coil

    the copper braid cable to the other end of the coil

    plut the audio cable into an amp and download NCH tone generator or similar

    rack up to volume to max (you might need a second amp to get enough juice)

    put a neodymium magnet in the middle and watch it skip around at whatever frequency you wish, you can go from 1 to 22000 Hz I think.

    Hope that helps, i think it's a pulsed DC current electromagnet? i don't call myself a scientist but thought it might be interesting as no one mentioned pulsed DC for adjusting EM frequency.

    Also, could use the audio output to power a small low power laser, connected to a LDR and a 12v battery, then you could pulse the coil with more juice..
     
    Last edited: Feb 16, 2012
  13. Feb 16, 2012 #12

    LURCH

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    If I understand your question correctly, then the answer is actuaaly "no". This would also mean that the previous response of "yes" was a missunderstanding of your question. For example, 60Hz goes into a lightbulb, but what comes out is everything from 400–800 terahertz (visible light); plus a lot more (bulb gets hot). Is that what you're asking about?

    As an example, could you explain how this relates to the functioning of the lightbulb mentioned above? Specifically; how there's a generator at the power plant, but there's also the filiment in the bulb...

    I think you could explain it better than I.
     
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