Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Generators: Water instead of a coil?

  1. Aug 20, 2004 #1
    Yea, I just had a pretty wierd idea, can we instead use water instead of a coil since water is a conductor as well (impure water that is.). Can we instead rely on convection currents or water waves to power this generator?
  2. jcsd
  3. Aug 20, 2004 #2
    I not sure I understand...are you saying we should use water with electrolytes instead of a coil of wire in the generators? How do you expect the water to help produce greater electricity if you cant even coil it. Having the coil move through the magnetic field can generate a lot more power than electrolites in water. Besides, copper for example is a lot more conductive than water with ions.
  4. Aug 20, 2004 #3
    Actually, I'm saying that the water acts as a coil in a conventional generator, and the movement of the water actually cuts the magnetic field which induces a current in the water. I'm not sure exactly how, and have no idea how a system using this thing I thought can be engineered yet, but is it theoretically sound?
  5. Aug 20, 2004 #4


    User Avatar
    Science Advisor

    Perhaps a different use for hydroelectric dams? The motion of the water is supplied by the current?
  6. Aug 20, 2004 #5


    User Avatar
    Science Advisor
    Gold Member

    Where would you put the water?

    And, how will you avoid water vaporization?.

    I could help you more if you explicit it more geometrically (i.e water flowing).
  7. Aug 21, 2004 #6
    Using water in place of a coil is a terrible idea. Generators work by spinning a roter in the magnetic field of permanent magnets. The rotor has a coil of conductive wire, and as a conductor is moved through the magnetic field by spinning, it causes the flow of electrons in the conductor, which is a current. Using water to move through the magnetic field wouldnt give nearly the same amount of current, im not even sure if ANY current would be produced. Although some current should be produced if the water has electrolytes in it, but once again im not too sure.
  8. Aug 21, 2004 #7


    User Avatar
    Staff Emeritus
    Science Advisor

    There's some research into magnetohydrodynamic propulsion for ships, using seawater. For instance

    http://www.sanu.ac.yu/English/Shipbuilding/Tema4.htm [Broken]

    But I've never heard of any serious interest in MHD generators, at least for sewater. There's some interest in MHD generators using plasma as the conducting medium. Google finds for instance the explosive magnetohydrodynamic generator


    The goal is apparently to provide a power supply for high power pulsed microwave devices, which could be used to burn out electronics
    Last edited by a moderator: May 1, 2017
  9. Aug 21, 2004 #8
    Well, while I agree that you can't really replace coils with water, liquids are used in sophisticated technology that requires really good conductivity. Liquid Hydrogen is used in MRI machines, as a way of conductivity. It's just that it would be more expensive, and probably more fragile, to use water as a conducter instead of a coil. I'm not sure, but I believe some metals have better conductivity, than water anyways.
  10. Aug 22, 2004 #9
    That makes sense because liquid hydrogen is at almost obsolute zero, which means any current that goes through it will have very very little resistance, making it very conductive. Now that i think about it, it would be awsome to have a coil of wire in a generator which would be surrounded by a tube filled with liquid hydrogen/nitrogen/helium, using liquid nitrogen would be the least expensive. In fact I beleive that people are planning to make the power lines that take electricity to homes have that kind of tube around it filled with some cold substance. If power lines are made that way, they would be able to power (im guessing) thousands more homes. Since I=V/R, at almost absolute zero R is very small, which gives a huge current. If absolute zero is ever achived in the wires, then the resistance would be 0, therefore I=V/0 = infinity, you would have infinite current.
  11. Aug 22, 2004 #10
    Water in its pure state doesn't conduct electricity at all. There has to be ions in the water to carry the current.
  12. Aug 22, 2004 #11


    User Avatar
    Staff Emeritus
    Science Advisor

    Like, for instance, sea water, which has salt.
  13. Aug 23, 2004 #12
    Yes, and with water you have many problems because theres only so much you can disolve in it in order for it to have ions. While with metals, you dont have the problem since its already conductive and plus is can be made superconductive if cooled.
  14. Aug 23, 2004 #13
    You can generate electricity using the difference in temperature at the surface of the sea and deep down.It has been tested near Hawaii somewhere.Don't ask me where.
  15. Aug 24, 2004 #14


    User Avatar
    Staff Emeritus
    Science Advisor

    The main attraction of MHD propulsion systems that attracts research interest is that they are potentially very quiet. See for instance "Red October". But they aren't the greatest as far as effeciency goes. Providing the intense magnetic field they need is a problem as well.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook