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Motion, Forces, & Energy

  1. May 1, 2006 #1

    A lamp hit a black paper with a thermometer underneath, what two energy transfers are shown?

    1. I think the lamp to the black paper is radiant energy to thermal energy.
    2. Black paper to themometer I'm not sure about. Thermal energy to electrical energy?

    I need help!! :confused:
  2. jcsd
  3. May 2, 2006 #2


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    Light is a form of electromagnetic radiation, so it is radiating energy outward to the black paper.
    When the light hits the paper, energy is absorbed into the paper raising its temperature. You could call this thermal energy I suppose, but if you take into account that the temperature of an object is a measure of the average kinetic energy of the particles...you could also call it kinetic energy as well.

    Electrical energy --> Thermal energy --> Electrolmagnetic radiation (light energy) --> Thermal Energy
  4. May 2, 2006 #3
    Oh thank you, but let me clarify this.
    Electrical energy from the thermometer, thermal energy from the black paper, and electromagnetic energy from the lamp?
    I don't quite understand the order you put the energies in:
    Electrical energy --> Thermal energy --> Electrolmagnetic radiation (light energy) --> Thermal Energy.
    Last edited: May 2, 2006
  5. May 2, 2006 #4


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    For the purposes of this diagram, we assume the energy starts out as electrical energy to power the light bulb. The electrical energy is converted into heat energy as the filiment glows which intern radiates electromagnetic energy. The light then heat up the black paper, turning electromagnetic energy back into heat/thermal energy. Some of the heat from the black paper is transfered into the thermometer, but it stays as heat energy, it does not change forms again (unless it is one of those thermo couple thermometers which opperate of an electric current generated by two metals of different temperatures...lets just assume it is an old fashion thermometer for simplicity sake).
  6. May 2, 2006 #5
    why does i appear in the wave equation.

    please help
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