What is a Joule Second? - Explained Easily!

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SUMMARY

A joule second is defined as the unit of action and angular momentum, crucial in physics, particularly in quantum mechanics. It represents the product of energy (joules) and time (seconds), contrasting with joules per second, which indicates power. The discussion highlights the relationship between joule seconds and Planck's constant, emphasizing that energy cannot be transferred in less than a specific time frame dictated by this constant. Understanding joule seconds is essential for grasping concepts like the least action principle and energy transfer in physical systems.

PREREQUISITES
  • Understanding of basic physics concepts, particularly energy and work.
  • Familiarity with Planck's constant and its significance in quantum mechanics.
  • Knowledge of angular momentum and its applications in physics.
  • Basic comprehension of the least action principle in physics.
NEXT STEPS
  • Research the implications of Planck's constant in quantum mechanics.
  • Explore the least action principle and its applications in classical and modern physics.
  • Study angular momentum and its role in atomic models, particularly the Bohr atom.
  • Investigate the relationship between energy transfer and time in physical systems.
USEFUL FOR

Students and professionals in physics, particularly those studying quantum mechanics, as well as educators seeking to explain complex concepts like action and energy transfer.

cnidocyte
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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?
 
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It is the unit of action -- as in the least action principle.

It is also the unit of angular momentum -- cf. the Bohr atom.
 
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.
 
cnidocyte said:
[...] but what in the name of God is a joule second?

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 -
N*dE*dt

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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