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Energy neither created nor destroyed

  1. Mar 10, 2010 #1
    I am studying engineering in my preparatory year and i have an idea which i would like to know if it is true??
    why don't we connect a motor with a generator ??
    so if we rotated the generator with our hand , the current produced will go to the motor which will rotate due to the magnetic forces and will rotate also the generator......
    so it will not stop....
    but does that agree with the theory of energy :"Energy neither created nor destroyed but it can be transformed with one form to another"
  2. jcsd
  3. Mar 10, 2010 #2


    Staff: Mentor

    Re: generator+motor

    Hi Super.man, welcome to PF.

    Perpetual motion machines are not an accepted topic for PF. It won't work because it will take more energy to turn the motor than the generator will produce.
  4. Mar 10, 2010 #3
    Re: generator+motor

    can't i use any circuit to increase the current produced by the generator and hence increase the power .
  5. Mar 10, 2010 #4
    Re: generator+motor

    yes but then the motor will require more power.....to drive a generator, you need to produce power in a way that utilizes other power sources instead of electricity...say water falling (hydroelectric power), burning fossil fuels (a diesel engine or a gas turbine) or wind...
  6. Mar 10, 2010 #5
  7. Mar 10, 2010 #6
    Re: generator+motor

    I get it now...
    Thanks for explaining :cool:
  8. Mar 10, 2010 #7
    Re: generator+motor

    LOL! I remember doing this as a kid. I didn't expect it be an "eternity machine", but I did wonder if the motor would run longer by a measurable time on my clock :-)

    I used a motor from a radio controlled car, and a generator from a bicycle, and connected them with a rubber belt. The amount of friction was quite high.... I couldn't detect a difference, of course :-)

    Really cool that this post reminded me of my scientific endeavors as a young boy.

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