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Whats a joule second?

  1. Jul 9, 2010 #1
    I can easily picture joules per second (I just see light of varying intensities passing a point at varying rates) I don't know what a joule second is. I know that Plancks constant is just to use the frequency of the photon to find out its energy but what in the name of God is a joule second?
  2. jcsd
  3. Jul 9, 2010 #2
    It is the unit of action -- as in the least action principle.

    It is also the unit of angular momentum -- cf. the Bohr atom.
  4. Jul 9, 2010 #3


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    Staff: Mentor

    A joule in mechanical work is 1 N of force applied on an object to move it a distance of 1 m. So a joule persecond is doing the above action in one second.

    Btw, a "joule per second" and a "joule second" are not the same thing. Jule per second is dividing by seconds, joule second would be multiplying by seconds.
  5. Sep 14, 2010 #4
    If i understood correctly you can consider this example:

    you can boil 1 m^3 of water by transferring to it N*dE energy in a 1 second OR
    you can boil 1 m^3 of water by heating water N*dt time with 1 joule of energy

    and thus we can define minimal action needed for 1 m^3 water to be boiled -

    As about Plank constant we can interpret it also like this:
    you can't transfer less energy than h in 1 second OR
    you can't transfer 1J of energy in less than h seconds.
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