### h-bar

Posted:

**Tue Apr 17, 2018 7:49 pm**In the Heisenberg uncertainty equation, does h-bar basically mean plancks constant divided by 2pi? Will this number always be the same/constant or are there instances where its different?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=19&t=30874

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Posted: **Tue Apr 17, 2018 7:49 pm**

In the Heisenberg uncertainty equation, does h-bar basically mean plancks constant divided by 2pi? Will this number always be the same/constant or are there instances where its different?

Posted: **Wed Apr 18, 2018 2:03 pm**

h bar is always

Posted: **Wed Apr 18, 2018 2:10 pm**

Will we need to memorize the value of h-bar on the test next week?

Posted: **Fri Apr 20, 2018 2:31 pm**

Since on Test #1 we are given many formulas we did not need for that test specifically, I think we can assume h bar will not be specifically given. The formula sheet does include the value of Planck's constant and pi so you can easily use that information and your knowledge of h bar to find the value needed.

Posted: **Fri Apr 20, 2018 7:53 pm**

If h-bar is h/ 2*pi, where does the h/ 4*pi come from in the Heisenberg Indeterminancy Function come from?

Posted: **Sat Apr 21, 2018 12:13 pm**

I was also confused between the practicality of using instead of . What is the difference between the two?

Posted: **Mon Apr 23, 2018 3:15 pm**

h-bar is used because it is a common value for use with the Schroedinger equation. is a derived quantity in the Heisenberg equation, but it is not represented with a special character because it does not show up as commonly in quantum mechanical equations compared to h-bar.

Posted: **Sun Apr 29, 2018 1:59 pm**

The Uncertainty Equation stated in the textbook has 1/2 * h-bar, and since h-bar is h/2pi, we use h/4pi.