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Uncertainty principle and electromagnetic field

  1. Sep 7, 2010 #1
    hi,

    I have a question about the uncertainty principle.

    if an electron is in attractive OR repulsive electromagnetic field, is its uncertainty about its position lower than if it is a free electron?

    I believe particles are more random, with a higher entropy when there is less interaction.
    Am I right?
     
  2. jcsd
  3. Sep 8, 2010 #2

    tom.stoer

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    Science Advisor

    The Heisenberg uncertainty principle gives you a lower bound of the "uncertainty in position space" times "uncertainty in momentum space".

    If you have an electron in a certain potential you have to solve for the wave function and calculate the two uncertainties explicitly. It can very well be that one uncertainty is rather small, whereas the other one becomes large. But the lower bound as specified in the Heisenberg uncertainty principle is never violated.

    A simple state which minimizes the uncertainty relation is the ground state of the harmonic oscillator. You can by no means reduce the uncertainty.
     
  4. Sep 8, 2010 #3
    Adding to the above: Uncertainty relations concern preparation procedures of quantum states. They also apply to possible measurements at a given time. They have nothing to do with the dynamics. They deal with kinematical variables.

    Time-energy uncertainty relation is somewhat different - it has its own treatment. It has been discussed elsewhere. But this is not what you are concerned with.
     
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