Maintaining Quasi neutrallity - a question.

MSimon · Post by **MSimon** » Sat Jul 18, 2009 10:39 pm

Aero wrote:But Simon, that will get complicated. What if it hails, hailstones are reported in penny sized, quarter sized, golf ball, baseball and softball sized. I'm sure their speed of impact can be approximated by terminal velocity, but what is the keV of a quarter sized hailstone?

You'll need this so you can report the temperature, .025 eV, and the hailstones in keV, that is, consistent units.

Speed is not normally measured in joules.

icarus · Post by **icarus** » Sat Jul 18, 2009 10:40 pm

Aero: ... you're getting to the crux of my point. We can't do the weather in eVs but we can do fusion physics?

EDIT: "temperature is not normally measured in joules" .... energy, temperature, velocity what's the difference it's all eVs compatible right? Time-wasting, interpretive jobsworth jargonism.

Something doesn't add up here and using inconsistent units is some major rot in the basement for any scientific structure.

Aero · Post by **Aero** » Sun Jul 19, 2009 4:26 pm

But consistent units for hailstones could actually represent an advancement in the science. As indicated by the following quotes (taken out of context), the science could use some help.

The article, here:
http://ams.allenpress.com/archive/1520- ... 2-1773.pdf
does make for interesting reading, though far off topic. I recommend it to all who would like some light science entertainment.

- the hailstone shown in Fig. 1 weighed about 0.5 kg.
- the hailstone in Fig. 2 was actually the largest of the collection, having a mass of 610 g.
- fall velocities probably greater than 40 m s–1,
- The fall velocity of a ... hailstone was determined to be about 47 m s–1
- we do not find any decisive arguments regarding which end is up;

Now it is quite simple to calculate the range of kinetic energy of these hailstones using
E = 1/2 mv^2,
and converting it to eV units. (left as an exercise for the reader

)

icarus · Post by **icarus** » Sun Jul 19, 2009 7:58 pm

Since eVs have a good range of numbers for mental conversions, comparisons, etc, which I can absolutely see the sense and in a machine like the Polywell where it is natural to base considerations on electrons being accelerated in electric potential fields, then it would disambiguate by using;

eVE - (eVs of energy)
eVT - (eVs of temperature)
eVV - (eVs for a velocity of an electron)

and save the extraneous discussion or interpretation of context step that needs to go along with using them for all three ... along with avoiding the lazy abbreviation to simply Volt which also happens regularly and requires the disambiguation with the other volts. Particularly for those of us who haven't a clue but like to know what they read means what it says.

chrismb · Post by **chrismb** » Sun Jul 19, 2009 8:42 pm

icarus wrote:Since eVs have a good range of numbers for mental conversions, comparisons, etc, which I can absolutely see the sense and in a machine like the Polywell where it is natural to base considerations on electrons being accelerated in electric potential fields, then it would disambiguate by using;

eVE - (eVs of energy)
eVT - (eVs of temperature)
eVV - (eVs for a velocity of an electron)

and save the extraneous discussion or interpretation of context step that needs to go along with using them for all three ... along with avoiding the lazy abbreviation to simply Volt which also happens regularly and requires the disambiguation with the other volts. Particularly for those of us who haven't a clue but like to know what they read means what it says.

I'm not sure you understand what 'eV' means, then. It is a very specific use of SI units, not an SI unit in itself. The 'e' is unit charge, 1.6E-19C. The 'V' is a volt! Volts x charge = energy. Just like Volts x current = power. So writing 'eV' is just like writing, say 'VA' ...or 'Nm' or 'ms^-1' or any other combinatorial unit with SI derivation.

icarus · Post by **icarus** » Sun Jul 19, 2009 10:51 pm

chrismb: I'm quite sure you don't understand what I'm saying.

I know exactly what an electron-Volt, the definition is quite clear, albeit arbitrary.

The common use is completely ad-hoc and definitely not SI. Depending if there was an implicit division by boltzman's 'k', it could be an energy or a temperature or some even use it as a velocity and others just drop the 'e' altogether and use volts as an energy. It's fraught and your puzzled comment about this being a bizarre discussion shows where you're coming from.

EDIT: In fact you are plain wrong, the 'e' is not an SI unit.
http://en.wikipedia.org/wiki/SI_electromagnetism_units

Shall we start using N.m (torque) with an implicit division by Planck's constant (h-bar) to reference standard rotation rates?

Don't look down the structure gets shaky up this high.

chrismb · Post by **chrismb** » Sun Jul 19, 2009 11:02 pm

icarus wrote:chrismb: I'm quite sure you don't understand what I'm saying.

I know exactly what an electron-Volt, the definition is quite clear, albeit arbitrary.

The common use is completely ad-hoc and definitely not SI. Depending if there was an implicit division by boltzman's 'k', it could be an energy or a temperature or some even use it as a velocity and others just drop the 'e' altogether and use volts as an energy. It's fraught and your puzzled comment about this being a bizarre discussion shows where you're coming from.

EDIT: In fact you are plain wrong, the 'e' is not an SI unit.
http://en.wikipedia.org/wiki/SI_electromagnetism_units

Shall we start using N.m (torque) with an implicit division by Planck's constant (h-bar) to reference standard rotation rates?

Don't look down the structure gets shaky up this high.

Please yourself. I was just trying to emphasise that eV is charge x volts = energy. Done.