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+---- Thread: GBARC PRESIDENT PUBLISHED IN SARC NEWSLETTER (/showthread.php?tid=785)
GBARC PRESIDENT PUBLISHED IN SARC NEWSLETTER - VE3WI Dave - 2022-07-09
In the July-August edition of the Surrey BC ARC newsletter, our President John VA3KOT explains why a battery gains weight when charged, and calculates how much. John's article begins on page 57. (That's p57 of 128, SARC goes all out with their newsletters! Lots of good reading in them.).
If you find John's math scary, check out the chart on page 12 - that's REALLY scary!
https://bit.ly/SARC22Jul-Aug
73
Dave, VE3WI
RE: GBARC PRESIDENT PUBLISHED IN SARC NEWSLETTER - Rob_Walker - 2022-07-11
That would mean then that a watch you wound by hand would weight more than a watch that is unwound because of the energy stored in the spring. I first heard of this senario as far back as 2013.
Good job John!
RE: GBARC PRESIDENT PUBLISHED IN SARC NEWSLETTER - VE3WI Dave - 2022-07-11
Absolutely correct Rob. I feel a physics lesson coming on
A more practical example of mass-energy equivalence:
The mass of an atom is less than the sum of the masses of it's component protons & neutrons. The difference is called "binding energy". That's the energy required to separate a nucleus into a bunch of protons and neutrons. It's also the energy released when a bunch of protons and neutrons are assembled into a nucleus.
The binding energy per particle is highest for medium sized atoms like iron, and lower for heavy atoms like uranium, and also lower for very light atoms like hydrogen.
So if you take an atom of uranium and split it into two smaller atoms, that's equivalent to separating its nucleus into a bunch of protons and neutrons, and then assembling two smaller nuclei from them. Due to different binding energy, the two product nuclei together weigh a bit less than the original uranium atom, and a lot of energy is released.
Making the same argument, if you take a couple of hydrogen atoms and force them together to make one heavier helium atom, it weighs a bit less than the original hydrogen atoms, and a lot of energy is released.
Whence cometh fission bombs, fusion bombs (AKA thermonuclear), controlled nuclear fission (like the reactors at Bruce), and maybe someday, controlled nuclear fusion reactors.
73
Dave, VE3WI
RE: GBARC PRESIDENT PUBLISHED IN SARC NEWSLETTER - Rob_Walker - 2022-07-11
Thanks for that Dave! It comes down basically to the different electrostatic potential energy of the electrons in relation to the nuclei
RE: GBARC PRESIDENT PUBLISHED IN SARC NEWSLETTER - VE3WI Dave - 2022-07-11
Actually Rob, it's the differences in nuclear binding energy that causes the energy release in fission and fusion. Nuclear binding energy relates to the strong nuclear force that holds neutrons and protons together to make a nucleus. Electrons don't really figure into it.
I attached a chart of binding energy vs # of nucleons (protons + neutrons) in the nucleus. The binding energy is given in MeV per nucleon. MeV is millions of electron-volts, a standard energy unit used in physics. 1 MeV = ~1.6 x 10^-13 Joule. The peak binding energy is Iron-56, and the curve slopes down both ways from there, both for larger atoms and smaller atoms.
For fission, a U-235 atom at the far right with 235 nucleons splits into two smaller atoms, one typically smaller than the other (there are many elements formed, but for example Krypton-92 and Barium-141), plus spitting out 2-3 neutrons. The Kr and Ba are found to the left of Uranium on the chart so have higher binding energy. So if you sum the plus and minus binding energies, one fission releases about 200 MeV of energy, which is about 3.2x10^-11 Joules. You can do the E=mc^2 calculation to see how much mass is lost. Not much.
Same reasoning for hydrogen - helium fusion, but operating on the left hand side of the chart.
More interesting (?) factoids:
- the 200 MeV from one fission is said to be enough to make a grain of sand visibly jump, if you could arrange for that to happen
- to produce 1 watt of thermal energy (heat) takes about 3x10^10 fissions per second
- a Bruce reactor at high power makes about 2800 thermal megawatts. The efficiency of the steam turbine cycle results in only about 800 electrical megawatts out to the grid. The rest is used to warm Lake Huron.
No more physics lectures unless I get paid!!!
73
Dave, VE3WI
RE: GBARC PRESIDENT PUBLISHED IN SARC NEWSLETTER - VA3KOT John - 2022-07-12
(2022-07-09, 11:14:58)VE3WI Dave Wrote: In the July-August edition of the Surrey BC ARC newsletter, our President John VA3KOT explains why a battery gains weight when charged, and calculates how much. John's article begins on page 57. (That's p57 of 128, SARC goes all out with their newsletters! Lots of good reading in them.).I think that article already appeared in GBARC's own Feedback newsletter. I started a blog some months ago just as a place to store articles I had written for Feedback. I haven't really promoted the blog for that reason. A few weeks ago, John Schouten VE7TI, the editor of SARC's Communicator newsletter emailed me to say he had enjoyed reading my blog and would I like to have a regular column in his newsletter. The article submission date for the July/August issue was coming up so he used one of my existing blog posts. Now I have to come up with original content for both GBARC and SARC. I guess I am going to be busy.
If you find John's math scary, check out the chart on page 12 - that's REALLY scary!
https://bit.ly/SARC22Jul-Aug
73
Dave, VE3WI