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Homework Help: Energy changes

  1. Mar 17, 2005 #1
    i was being ask to describe the energy changes involved in the use of mobile phones and a television

    i m noot even sure i have fully understand the question,

    energy change? say in mobile phone, all i can think of is signal wave turns to electric pulse which then changes into digital data... but it seem rather to staright forward so is there any other changes/?/

    any energy invloves chemical or kinetic or potential ?

    Last edited: Mar 17, 2005
  2. jcsd
  3. Mar 17, 2005 #2
    Well for example in the case of a phone : let us say that A talkes to B over the phone.

    When A talkes, his vocal cords make the air-molecules vibrate : that is how sound is generated. So the energy from the soundwave (which is a pressure wave) needs to be converted into an electrical signal. This is done by making a little plate vibrate (inside the phone), each vibration is converted into an electrical signal using for example a little wire that moves in a fixed magnetic field (due to Maxwell's laws they will generate a current in a wire that moves)... So now, the pressurewave (translational and vibrational energy) is converted into mechanical energy and then in electrical energy. Then you phone-operator will convert this electrical signal into EM-radiation (again a wave) that goes to the receiver of the phone of B. Then the reverse process starts : EM-wave to electrical signal to mechnical signal to pressure wave that will make B hear your message

  4. Mar 18, 2005 #3
    umm interesting so for tv the digtal or anologo data from source (e.g tape, cd dvd ) is converted into eletric pulese , then our tv broadcast station converted electric plues into em-radiation then goes to reciever...and the goes

    (skiped the Cathode Ray Tube part which produce the image for standard tv, i dont think i ve done cathode ray yet)

    and i remmber in the process of broadcasting it requires a carrier, could anyone explain how exact this works? thx
    Last edited: Mar 18, 2005
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