What is a Joule Second? - Explained Easily!

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Discussion Overview

The discussion centers around the concept of a joule second, exploring its definition, significance in physics, and its relationship to other units such as joules per second. Participants delve into the implications of this unit in the context of action and angular momentum, as well as its application in energy transfer scenarios.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about the concept of a joule second, contrasting it with the more easily understood joules per second.
  • Another participant states that a joule second is the unit of action and angular momentum, referencing the least action principle and the Bohr atom.
  • A different participant explains that a joule per second represents a force applied over a distance in one second, emphasizing the distinction between joules per second and joule seconds as multiplication versus division of time.
  • Further elaboration is provided with an example involving boiling water, suggesting that energy transfer can be conceptualized in terms of joule seconds and the minimal action required for energy transfer over time.
  • There is a mention of Planck's constant, with interpretations suggesting limits on energy transfer in relation to time.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and interpretation of the joule second, with some agreeing on its significance in physics while others remain uncertain about its implications and applications. Multiple competing views on its definition and context exist, leaving the discussion unresolved.

Contextual Notes

Participants highlight the need for clarity regarding the definitions and relationships between joules, joules per second, and joule seconds, indicating potential limitations in understanding without further elaboration on these concepts.

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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