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Does this violate the Law of conservation of energy?

  1. Sep 18, 2012 #1
    If I were to pump water from my well (at my house) into the pressure tank that we have, it would require a certain amount of work. If I then turned on my faucet and had a small turbine generating an electric current, would that electric current (which I realize would be small, this is more for myself to understand the concept) just be required then when the pressure tank is re-pressurized....does that make sense?

    Basically, if I generate a current from the tap, does that current then get negated by an extra amount needed to re-pressurize the tank?

    Thanks in advance!
  2. jcsd
  3. Sep 18, 2012 #2
    1. Re-Read what you write before you post, that makes no sense.
    2. What is violating the law?

    The fact that everything in your question relates to mechanical activities I can say without understanding your description-- nothing violates the Law of Conservation of Energy (to answer your "subject" question).
  4. Sep 18, 2012 #3


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    Staff: Mentor

    I think you are asking if the current generated by the tap water is completely used up when pumping water back into the tank. If so, then yes, that current would be completely used up, and due to inefficiencies you would actually require more energy than you created to pump water back into the tank.
  5. Sep 18, 2012 #4
    A practical example relating to your question is pumping water into a reservoir during periods of low electrical usage and then releasing the water later during a period of high electrical usage.

    It takes more energy to pump the water up than is later produced when it is released, but because energy is recovered during peak usage it is a practical compromise. So it it NOT getting 'something for nothing', but the timing of the pumping and subsequent recovery can make it useful.
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