Find Electron Concentration with Mass Density: A Simple Solution

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Homework Help Overview

The discussion revolves around determining the electron concentration of an object, specifically a neutron star, based on its mass density of 7.0 * 10^17 kg/m^3. Participants explore the complexities involved in relating mass density to electron concentration, emphasizing the need for additional material composition information.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants question whether it is possible to find electron concentration with only mass density provided. Some suggest that knowing the material composition is essential, while others discuss the implications of the density being characteristic of a neutron star. There is also confusion regarding whether the inquiry pertains to neutrons or electrons.

Discussion Status

The discussion is active, with participants providing insights and raising questions about the assumptions underlying the problem. Some guidance has been offered regarding the complexities of the question, particularly in distinguishing between neutrons and electrons, but no consensus has been reached.

Contextual Notes

Participants note that the density suggests the object is a neutron star, which introduces additional complexities related to nuclear reactions and the behavior of free electrons in such dense environments. There is a lack of clarity regarding the specific nature of the inquiry, whether it pertains to electrons or neutrons.

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Is there a way to find the electron concentration of an object (N/V; number of free electrons per unit volume) given only that it's mass density is 7.0 * 10^17 kg/m^3? Thanks.
 
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ACLerok said:
Is there a way to find the electron concentration of an object (N/V; number of free electrons per unit volume) given only that it's mass density is 7.0 * 10^17 kg/m^3? Thanks.

The short answer is: no.

You need to know what it is made of!
 
ACLerok said:
Is there a way to find the electron concentration of an object (N/V; number of free electrons per unit volume) given only that it's mass density is 7.0 * 10^17 kg/m^3? Thanks.
That is extremely dense material - as in a neutron star.

One would have to know the nuclear reactions taking place in order to determine the equilibrium concentration for free electrons, which would ostensibly come from the decay of free neutrons.

Pulsars have free electrons - http://hyperphysics.phy-astr.gsu.edu/Hbase/astro/pulsar.html#c4

http://cassfos02.ucsd.edu/public/tutorial/SN.html - search for "free electrons" on the page

http://www.astro.soton.ac.uk/~bexmgr/xrpulsar.html
 
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Astronuc said:
That is extremely dense material - as in a neutron star.
Good point.. I had not paid attention to the exponent of the density:redface: when I read the question. I thought it was ordinary matter. Thanks for pointing this out.
 
Ohh, I forgot to mention that the object is indeed a neutron star. Would u just multiply that number above by the mass of a single neutron? I am stuck.. :/
 
ACLerok said:
Ohh, I forgot to mention that the object is indeed a neutron star. Would u just multiply that number above by the mass of a single neutron? I am stuck.. :/

Wait a minute!:smile:
Are you asking for the concentration of *neutrons* or of *electrons*?? If it is a question about neutrons, then it is extremely simple. If it is a question about electrons, then it is quite advanced and Astronuc gave some hints in that direction. It makes a huge difference...It goes from a high scholl level question to a physics undergrad (or higher) level question!

Patrick
 

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