| Topic: |
Science > Physics |
| User: |
"Stephen Bint" |
| Date: |
03 Nov 2003 07:09:16 PM |
| Object: |
The mass value of the electron-volt |
I have been trying to find out how the mass value of an electron volt was
determined, without any luck. Can anyone recommend a source of information
about the history and/or reasoning behind the common unit for mass and
energy?
Stephen
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| User: "Jon Bell" |
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| Title: Re: The mass value of the electron-volt |
03 Nov 2003 09:29:57 PM |
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In article <3fa6fbb7$0$106$65c69314@mercury.nildram.net>,
Stephen Bint <binty@iname.com> wrote:
I have been trying to find out how the mass value of an electron volt was
determined, without any luck.
The "electron volt" is a unit of energy, defined to be the energy gained
by a particle with one electron's worth of charge that is accelerated
through a potential difference of one volt. From baslc electromagnetic
theory, E = qV = (1.602 x 10^-19 coulomb)(1 volt) = 1.602 x 10^-19 joule.
According to relativity theory, a quantity of energy E corresponds to a
mass of E/c^2. (1.602 x 10^-19 joule)/(2.998 x 10^8 m/s) = 4.803 x 10^-11
kg = 1 eV/c^2.
Particle and nuclear physicists almost invariably use electron volts for
energy because because it relates directly to the way that they give
charged particles kinetic energy by accelerating them in an electric
field. An accelerator that uses a 200 kV potential difference to
accelerate electrons (or protons, etc.), gives them a kinetic energy of
200 eV apiece.
They use electron-volt units for mass because it simplifies calculations
involving mass, energy and momentum using E^2 = (mc^2)^2 + (pc)^2. They
also use electron-volt units for momentum, for consistency.
An electron (mass 511 keV/c^2) accelerated through 200 kV has a kinetic
energy of 200 keV, total energy of 200 + 511 = 711 keV, and a momentum of
pc = sqrt (E^2 - (mc^2)^2) = sqrt (711^2 - 511^2) = 494 keV, i.e. p = 494
keV/c.
Can anyone recommend a source of information
about the history and/or reasoning behind the common unit for mass and
energy?
I think most any freshman-level General Physics textbook or
sophomore-level Modern Physics textbook discusses this.
--
Jon Bell <jtbellap8@presby.edu> Presbyterian College
Dept. of Physics and Computer Science Clinton, South Carolina USA
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| User: "Stephen Bint" |
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| Title: Re: The mass value of the electron-volt |
03 Nov 2003 09:47:15 PM |
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"Jon Bell" <jtbellq2f@presby.edu> wrote in message
news:bo76fl$q6m$1@jtbell.presby.edu...
In article <3fa6fbb7$0$106$65c69314@mercury.nildram.net>,
Stephen Bint <binty@iname.com> wrote:
I have been trying to find out how the mass value of an electron volt was
determined, without any luck.
The "electron volt" is a unit of energy, defined to be the energy gained
by a particle with one electron's worth of charge that is accelerated
through a potential difference of one volt. From baslc electromagnetic
theory, E = qV = (1.602 x 10^-19 coulomb)(1 volt) = 1.602 x 10^-19 joule.
According to relativity theory, a quantity of energy E corresponds to a
mass of E/c^2. (1.602 x 10^-19 joule)/(2.998 x 10^8 m/s) = 4.803 x 10^-11
kg = 1 eV/c^2.
Particle and nuclear physicists almost invariably use electron volts for
energy because because it relates directly to the way that they give
charged particles kinetic energy by accelerating them in an electric
field. An accelerator that uses a 200 kV potential difference to
accelerate electrons (or protons, etc.), gives them a kinetic energy of
200 eV apiece.
They use electron-volt units for mass because it simplifies calculations
involving mass, energy and momentum using E^2 = (mc^2)^2 + (pc)^2. They
also use electron-volt units for momentum, for consistency.
An electron (mass 511 keV/c^2) accelerated through 200 kV has a kinetic
energy of 200 keV, total energy of 200 + 511 = 711 keV, and a momentum of
pc = sqrt (E^2 - (mc^2)^2) = sqrt (711^2 - 511^2) = 494 keV, i.e. p = 494
keV/c.
Can anyone recommend a source of information
about the history and/or reasoning behind the common unit for mass and
energy?
I think most any freshman-level General Physics textbook or
sophomore-level Modern Physics textbook discusses this.
--
Jon Bell <jtbellap8@presby.edu> Presbyterian College
Dept. of Physics and Computer Science Clinton, South Carolina USA
Thank you , Jon.
Stephen
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| User: "Timo Nieminen" |
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| Title: Re: The mass value of the electron-volt |
03 Nov 2003 10:06:20 PM |
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On Tue, 4 Nov 2003, Stephen Bint wrote:
"Jon Bell" <jtbellq2f@presby.edu> wrote:
Stephen Bint <binty@iname.com> wrote:
I have been trying to find out how the mass value of an electron volt was
determined, without any luck.
[cut]
Just adding:
AFAIK, the theory came first (Einstein, Ann. Phys. 18, p.639, 1905, you
might be able to find an English version on www) and experimental
measurements came later. Some of the early experiments were largely
qualitative, showing that energy could be transformed into mass (pair
production) and vice versa, but there is no lack of accurate quantitative
measurements, mainly involving nuclear physics, radioactivity, and
behaviour of fast particles in accelerators.
--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html
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| User: "Bill Rowe" |
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| Title: Re: The mass value of the electron-volt |
06 Nov 2003 10:50:25 PM |
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In article <bo76fl$q6m$1@jtbell.presby.edu>,
(Jon Bell) wrote:
According to relativity theory, a quantity of energy E corresponds to a
mass of E/c^2. (1.602 x 10^-19 joule)/(2.998 x 10^8 m/s) = 4.803 x 10^-11
kg = 1 eV/c^2.
The comments and equation are correct. But the numerical computation
shown is incorrect. The numerical calculation s/b
(1.602 x 10^-19 joule)/(2.998 x 10^8 m/s)^2 = 1.783 x 10^-36 kg
--
To reply via email subtract one hundred nine
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| User: "Sam Wormley" |
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| Title: Re: The mass value of the electron-volt |
03 Nov 2003 10:36:20 PM |
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Stephen Bint wrote:
I have been trying to find out how the mass value of an electron volt was
determined, without any luck. Can anyone recommend a source of information
about the history and/or reasoning behind the common unit for mass and
energy?
Stephen
Electron Volt, a quantity used in atomic an nuclear physics, representing
the work done if an elementary charge ia accelerated by a potential difference
of one volt.
1 eV = 1.602 x 10^-19 J
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| User: "Uncle Al" |
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| Title: Re: The mass value of the electron-volt |
03 Nov 2003 07:33:27 PM |
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Stephen Bint wrote:
I have been trying to find out how the mass value of an electron volt was
determined, without any luck. Can anyone recommend a source of information
about the history and/or reasoning behind the common unit for mass and
energy?
Jesus H. Christ,
Google
electron volt to grams
output is
1 electron volt = 1.78266173x10^(-33) grams
An electron volt is energy. E=mc^2. Crack your "CRC Handbook."
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
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| User: "Stephen Bint" |
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| Title: Re: The mass value of the electron-volt |
03 Nov 2003 08:55:23 PM |
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"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:3FA701E7.6802DD0D@hate.spam.net...
Stephen Bint wrote:
I have been trying to find out how the mass value of an electron volt
was
determined, without any luck. Can anyone recommend a source of
information
about the history and/or reasoning behind the common unit for mass and
energy?
Jesus H. Christ,
Google
electron volt to grams
output is
1 electron volt = 1.78266173x10^(-33) grams
An electron volt is energy. E=mc^2. Crack your "CRC Handbook."
--
Uncle Al
That is not the answer to my question. I want to know how how it was
determined that
1 electron volt = 1.78266173x10^(-33) grams
Jesus H. Christ,
Exapseration at the stupidity of others is not a product of intelligence,
nor wisdom, but of vanity.
Stephen
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| User: "Richard" |
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| Title: Re: The mass value of the electron-volt |
03 Nov 2003 10:18:54 PM |
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Stephen Bint wrote:
"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:3FA701E7.6802DD0D@hate.spam.net...
Stephen Bint wrote:
I have been trying to find out how the mass value of an electron volt
was
determined, without any luck. Can anyone recommend a source of
information
about the history and/or reasoning behind the common unit for mass and
energy?
Jesus H. Christ,
Google
electron volt to grams
output is
1 electron volt = 1.78266173x10^(-33) grams
An electron volt is energy. E=mc^2. Crack your "CRC Handbook."
--
Uncle Al
That is not the answer to my question. I want to know how how it was
determined that
1 electron volt = 1.78266173x10^(-33) grams
Jesus H. Christ,
Exapseration at the stupidity of others is not a product of intelligence,
nor wisdom, but of vanity.
Stephen
An electron volt is just the energy gained by an electron when traveling
through a potential difference of 1 volt. The mass equivalent of that
energy is given by
E = mc^2.
OTOH, the equation can be interpreted much differently than the standard
interpretation. According to my own derivation of this equation, it
expresses a relationship between the energy and the mass of a sample of
neutral matter, not an equivalence. Note also that an equivalence would
require the term c to be dimensionless, thus simple logic supports this
interpretation. Similarly the number of fingers per hand is a constant
ratio, but this in no way implies that a hand is equivalent to fingers,
the palm and thumb are also required in order to make a hand.
Analogously mass requires the additional element of the speed of light
squared in order to make rest energy. IOW the fundamental particles of
which the matter is composed are moving at an average speed of c wrt
the object that they compose. This necessity is also derived
mathematically in my paper, and is in fact prerequisite to the
derivation of E=mc^2. Thus either the fundamental particles of matter
are massless, and are bosons, or SR is incorrect in that the alternative
is that massive particle can and do propagate faster than c. OTOH there
is a third option, that fundamental charges are neither massive or
bosons, but mass is instead a property only of systems of these
particles, which latter is preferred by the E=mc^2 relationship in that
E is just the electromagnetic PE in my derivation of the equation.
Electromagnetic PE in turn requires more than the existence of a single
quanta of charge, it requires at least two of them in relative motion.
An orbit will do, and when two such particles are placed into a common
orbit then the equation E=mc^2 describes the mass energy ratio of that
system. IOW it only applies to atomic, or 'neutral' matter.
Richard Perry
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| User: "Dan Bloomquist" |
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| Title: Re: The mass value of the electron-volt |
03 Nov 2003 09:08:49 PM |
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Stephen Bint wrote:
That is not the answer to my question. I want to know how how it was
determined that....
This was discussed in depth over the last few days. Why not go back and
read it?
Best, Dan.
--
http://lakeweb.net
http://ReserveAnalyst.com
dbAtLakewebDotCom
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