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Microwaves and Electro-magnetic waves (lame questions!)

  1. Mar 31, 2012 #1
    Microwaves are said to be Electromagnetic waves with frequency 300 Mhz to 300 Ghz.
    If so, then, is the CPU of my computer running at 2Ghz, emitting some sort of microwave ? Is the microwave cooking tiny drops of water around ?
    (I say so, because, if the CPU is running at 2GHz, currents must be pulsing at 2Ghz, and that might create EM wave at 2Ghz).
    Also, if I make some resonant electric Circuit to oscillate at 500 Thz, will I see some 'Red Lights' .
    Also, if I static charge my plastic pen by rubbing against my hair, and then 'Wave' this charged pen at round 3 hz, will I be creating Radio Waves at 3hz ?
    Thanks for reading.
     
  2. jcsd
  3. Mar 31, 2012 #2

    marcusl

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    Yes, but at very low efficiency. The CPU microchip is a poor radiator because currents and their return paths (grounds) are very very close to each other. In other words, the sources are not connected to a good antenna.
    Well, yes if there is water nearby. The amount of power is absolutely tiny, however.
    Yes
    Yes, but, again, this is a very weak source.
     
  4. Mar 31, 2012 #3
    Thanks marcusl.
    Well, its a pleasure to hear a 'Yes', to all of the questions. It saves me from 'editing' my knowledge. (Because, 'Yes' was what I was expecting). :)
     
  5. Apr 1, 2012 #4
    Sorry, but your answers are incorrect - the 2 GHz refers to a clock speed at which the computer is running, not electromagnetic waves. If you have a watch that ticks of seconds, you can say the clock speed is 60 Hz (60 cycles/second) - that happens also to be the frequency of the AC voltage at your wall plug. That's a coincidence; they are not related, i.e. your watch and the AC voltage.
     
  6. Apr 1, 2012 #5
    Part of the circuit in CPU actually runs at 2GHz, be it a small part, it can potentially emit EM wave at 2GHz be it very weak. Clock speed running meaning there is EM wave at 2GHz.

    Remember AC electrical signal IS really EM wave propagation, not current or voltage travelling in the straight sense. Remember electrons move very slow, if it is current or voltage moving, things are very slow. The reason signal move in conductor at great speed BECAUSE it's the EM wave that propagates. Voltage and current measured are the consequence of the boundary condition of the EM wave in the transmission line....it this case, the traces inside the CPU.

    Any imperfection in the guided structure, EM wave radiates out.......most traces are microstrip and they leak!!!...Even inside the IC.
     
    Last edited: Apr 1, 2012
  7. Apr 2, 2012 #6
    surely any cpu clock running at 2 GHz is going to be an electrical oscillation at 2 GHz? so despite being very low power, and designed to pass EMC tests the principle is the same.

    is a 500 THz tank circuit possible? that might be incredibly efficient lighting!
     
  8. Apr 2, 2012 #7
    I forgot to mention, the signal inside the CPU are all square or pulses with very fast rise time. Even the fastest 2GHz clock is sort of like a square wave and has odd harmonics. So I won't be surprised it has 6GHz and 10 GHz harmonics. Other slower frequency signals has high speed edge also and will have harmonics.

    Inside the CPU, even it's an IC, it has traces just like pcb, mostly microstrip that radiates. ON top, it behave just like pcb where emission happen when signal goes from one layer to the other and if the image current is not following, you have emission.
     
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