-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
JohnEC
S 00443
OK, I'm no expert either, but I really don't believe that E=mc^2 applies here. We're not converting matter into energy. No nuclear reactions, just simple chemistry. Perhaps we could get a real physicist or even a chemical engineer to chime in??
From my rudimentary understanding, it doesn't matter what kind of energy conversion happens. Energy has a "weight", that's one of the things E=mc² expresses.
So if you take 2 configurations with the same amount/kind of matter but with different amounts of stored energy, they should end up with a weight difference because there "is energy in the one and not in the other". As discussed before tho, the weight is rather small.
But, I'm not an expert on the matter. (I'm an electrical engineer... I guess I should be one though >.<)
Last edited:
It doesn't matter (no pun intended), enegy-mass equivalence is a fundamental law and makes no assumptions on the form the energy takes. We ARE converting matter iinto energy.
wraithnot
Model 3 VIN #2942 Model S VIN #5785
Here is a relevant paragraph from the wikipedia page on mass-energy equivalence:
The difference between the rest mass of a bound system and of the unbound parts is the binding energy of the system, if this energy has been removed after binding. For example, a water molecule weighs a little less than two free hydrogen atoms and an oxygen atom; the minuscule mass difference is the energy that is needed to split the molecule into three individual atoms (divided by c²), and which was given off as heat when the molecule formed (this heat had mass). Likewise, a stick of dynamite in theory weighs a little bit more than the fragments after the explosion, but this is true only so long as the fragments are cooled and the heat removed. In this case the mass difference is the energy/heat that is released when the dynamite explodes, and when this heat escapes, the mass associated with it escapes, only to be deposited in the surroundings which absorb the heat (so that total mass is conserved).
This applies to all types of energy. It's just much easier to measure experimentally in nuclear reactions than in other situations.
Mark Petersen
Model S EU P71
I believe Ferrari have been researching in this for years
The more potent a car it the younger the driver will feel, that is way you will see many men in there 40's go out and buy super cars, in an attempt to become younger
me included, it is just an electric super car, as I believe electric will be even more potent than gas, as everybody say that living ecological will help prevent aging
HankLloydRight
No Roads
Maybe there's something I'm missing here.. according to several articles (like this one: How does a lithium-ion battery work, and why are they so popular? | ExtremeTech) that when the Lithium ions that are missing an electron are bonded to the lithium cathode in a discharged state, charging them then adds electrons back to the ions and they migrate and bond to the carbon anode to store the charge.... and when their electrons are given off during discharge, the ions migrate back to the cathode once again. So it does seem to me that electrons are being added to, and removed from, the batteries. So this describes the Lithium ions moving back and forth between the anode and cathode giving off or taking electrons along the way... it's not just electrons moving between them.
eta: nevermind, I get it now. The electrons take the long way around and are rejoined with the ions on the other side.
eta: nevermind, I get it now. The electrons take the long way around and are rejoined with the ions on the other side.
Last edited:
ra-san
Member
So where did the 3.4 micrograms of mass come from and go to?
What mass was transferred, created or destroyed (changed to/from energy) at charge time? At discharge time?
What mass was transferred, created or destroyed (changed to/from energy) at charge time? At discharge time?
All energy has mass. The extra 3.4 micrograms of chemical potential energy came from the source of the electricity used to charge the battery (e.g. grid or solar). As the battery discharges, this mass is first converted into kinetic energy (which also has mass) and then lost to the environment primarily has heat (rolling resistance, air resistance, braking, etc.). Heat also has mass.
Charging does not add electrons to the car because the number of electrons flowing into the battery is almost exactly equal to those flowing out (otherwise, the car would develop a strong negative charge).
Last edited:
Mass and energy are exchangeable. Energy can be converted into matter and matter into energy. Einstein's famous equation tells us that and it can be measured in the real world, even though it is usually very small amounts. One gram of matter is the equivalent of the amount of energy that could power a major city for a day.
dhrivnak
Active Member
I really think the answer is 0 as when charging you move electrons from the cathode to the anode. Then as you run the car the elections migrate to the cathode. The batteries are closed loop.
ra-san
Member
the point of my question goes to the implication by some of the others in this thread that if you measured an empty battery then a charged battery that you'd get a weight difference (won't go down the weight vs. mass angle here - assume assume a frictionless spherical cow in the same gravitational conditions ...).
I don't think so.
The answer of original source of energy and final destination sounds most right - though the example of solar doesn't quite work unless we look partially to the sun, not just the panels, right? Anyway, this thread has been an interesting diversion. Glad it was brought up.
I don't think so.
The answer of original source of energy and final destination sounds most right - though the example of solar doesn't quite work unless we look partially to the sun, not just the panels, right? Anyway, this thread has been an interesting diversion. Glad it was brought up.
Just as any particle flying through an accelerator (e.g. Large Hadron Collider) becomes heavier when the Accelerator pumps more energy into it (by making it fly faster), same happens with our cars. When you charge it, the energy from the grid becomes stored in the car, and this energy has mass. You can say the mass came through the wire, but it came in form of energy, not matter.
Notice that this energy was taken from the outside world when you charged. Which means the rest of the world became lighter. At some point almost all of it was lost by the Sun: converting Hydrogen into Helium, what it's currently doing, generates a significant mass deficit, which of course flies away in form of radiation energy. This energy got captured here on Earth either by the water (evaporated -> got higher up -> condensed -> melted -> gravity took it down -> spun the turbine in the hydroelectric plant) or by plants (photosynthesis created energy-rich, heavier, molecules that we burned many millions years later -> heated water -> spun the turbine in thermal power plant) or by air (it got warmer one place than the other and started moving to the colder areas -> spun the wind turbine) or by photovoltaic panel. The only exception here is the nuclear power plants that derive energy from extra mass captured in heavy elements generated by supernova explosions that happened in the previous generation stars.
When you drive, most of the energy is lost to air drag. This drag makes the air and the car a little warmer, and therefore heavier. While the battery becomes liter, the world around it becomes heavier as you drive.
HankLloydRight
No Roads
Wow, romp.. That's heavy
- - - Updated - - -
From what I understand, it's actually the Lithium Ions that shuttle between the anode and cathode, pushing the electrons through the load(motor) when discharging, and the opposite when charging.
- - - Updated - - -
From what I understand, it's actually the Lithium Ions that shuttle between the anode and cathode, pushing the electrons through the load(motor) when discharging, and the opposite when charging.
During a road trip and measuring the total vehicle weight, If you stop at a rest stop and drop some friends off in the toilet during a bathroom break the total vehicle weight while driving will now weigh less than the difference between a fully charged MS vs non empty one. That be some science for you.
astrothad
Member
Real physicist chiming in - yes, E=mc^2 applies, even with electron binding energies rather than nuclear binding energies. It's just much smaller, as the correct calculations already done in this thread show. If we take 85 kWh as having 2 significant figures, than 3.4 micrograms of additional mass is the correct answer. However, when compared with a car that has a curb mass of 2.1 trillion micrograms...
