For Questions That Don't Merit Their Own Thread

[Kryten]

When you see a blackout moving, that's not really anything to do with the speed of electricity, that's just the power grid shutting down section by section. The actual speed of electricity depends on a bunch of factors like the material it's travelling through, but in real-world conditions it'll pretty much always be a double-digit percentage of the speed of light.

[Aghanim]

So I'm wondering about quench gun, which is basically coilgun that stores its energy on superconducting coils and quenching it to kill the magnetic field, allowing the projectile to be pulled to the next coil. Lets say we have a magic lossless switch that can dump the energy into a magical lossless capacitor, so that we can collapse the magnetic field without wasting all the energy inside the coil, as we can use the stored energy in the capacitor to recharge the coil. If we connect the end of this quench gun to the other end, making a loop, will this creates infinite energy?

If we replace all the magical device with real devices that have resistance, is recapturing the energy worth it instead of just quenching the superconducting coils?

 

 

[p1t1o]

9 hours ago, Aghanim said:

...will this creates infinite energy?

NO.

Not even with magical lossless components, as you have described a lossless cycle with no energy input.

At best, as long as you are not using substandard magic, the cycle could run forever.

In reality all you have built is the worlds most expensive space heater

 

Edited September 28, 2016 by p1t1o

[K^2]

The answer is always no, of course, but it's an even bigger no in this case. Quenching takes superconductor to normal phase, which means it becomes a resistor. In turn, that means it's guaranteed to dump all of its energy as heat. There is absolutely no way to recover that with capacitors, magical or otherwise, since heat is generated in the former superconductor itself.

It is possible to use superconductors to convert between mechanical and electrical energy almost flawlessly. But that still doesn't give you a way to generate extra energy. Nothing does. Such is the fundamental symmetry of our space-time. Not that it can't be fun and/or educational to figure out why such things don't work.

[shynung]

Why is methane a gas, but methanol a liquid at room temperature? What's in the OOH branch that makes methanol a liquid at room temperature, where methane isn't?

[peadar1987]

7 minutes ago, shynung said:

Why is methane a gas, but methanol a liquid at room temperature? What's in the OOH branch that makes methanol a liquid at room temperature, where methane isn't?

It's got to do with the "balance" of the molecules. Methane is symmetrical, so the only forces between the molecules are "van der Waal's Forces". Basically the electrons move at random, and sometimes there are more at one side of the molecule than the other. That causes what is known as a "dipole". Negative dipoles and positive dipoles attract each other, so that pulls the molecules closer together. Methane doesn't have that many electrons, so there aren't that many dipoles in existence at any one time, so the molecules aren't that strongly attracted to each other overall. Bigger molecules like octane have far more electrons, and therefore far more dipoles at any one moment in time, so the molecules are more strongly attracted to each other. This raises the boiling point of the compound because you have to put in more energy to cause the molecules to overcome the forces between them and fly apart from each other.

Methanol is different because it is asymmetric. Hydrogen has a much greater affinity for its electrons than oxygen does, so the electrons will spend far more time close to the hydrogen than the oxygen. This sets up a permanent dipole, as opposed to the temporary, random dipoles that cause van der Waal's forces. This means that the molecules in methanol have a far greater attraction to each other than the molecules in methane. The extra electrons from the oxygen will also increase the van der Waal's forces as well.

This is the very basic version, others with a chemistry background could probably go into more depth, but hope it helps.

[p1t1o]

28 minutes ago, peadar1987 said:

It's got to do with the "balance" of the molecules. Methane is symmetrical, so the only forces between the molecules are "van der Waal's Forces". Basically the electrons move at random, and sometimes there are more at one side of the molecule than the other. That causes what is known as a "dipole". Negative dipoles and positive dipoles attract each other, so that pulls the molecules closer together. Methane doesn't have that many electrons, so there aren't that many dipoles in existence at any one time, so the molecules aren't that strongly attracted to each other overall. Bigger molecules like octane have far more electrons, and therefore far more dipoles at any one moment in time, so the molecules are more strongly attracted to each other. This raises the boiling point of the compound because you have to put in more energy to cause the molecules to overcome the forces between them and fly apart from each other.

Methanol is different because it is asymmetric. Hydrogen has a much greater affinity for its electrons than oxygen does, so the electrons will spend far more time close to the hydrogen than the oxygen. This sets up a permanent dipole, as opposed to the temporary, random dipoles that cause van der Waal's forces. This means that the molecules in methanol have a far greater attraction to each other than the molecules in methane. The extra electrons from the oxygen will also increase the van der Waal's forces as well.

This is the very basic version, others with a chemistry background could probably go into more depth, but hope it helps.

Actually as a chemist I was going to give a far simpler version! You gave pretty good coverage over the electronic effects of having an oxygen present - The only thing I'd add is that simple ol' mass has a significant effect on melting/boiling points. And going from methane -> methanol, just that one extra oxygen doubles the mass of the molecule.

...although now that I read more closely...I see that you have got the hydrogen bonding backwards (though your basic concept is correct, and the VdW explanation good) - oxygen is electron-rich, its outer shell is almost full, and 4 of its outer electrons are in nice comfortable pairs. These pairs are available to form a sort-of "pseudo bond" with any electron-deficient areas on neighbouring molecules. Hydrogen has a strong affinity for its electrons, but it is electron-deficient, all of its electrons being involved in the bond it is involved in. Thus there is a delta-positive and a "lone pair" from a nearby oxygen will be able to make a bond here.

The rule is "FON". Fluorine, Nitrogen and Oxygen have an abundance of electrons and have these "lone pairs" in their outer shells which are able to bond to hydrogen, forming the "pseudo bond" known imaginatively as a "hydrogen bond". These bonds can be as strong as a regular covalent bond in some cases, but are often significantly weaker, depending on the molecular structures involved. The exact geometry and makeup of whatever molecule will also have an effect on the degree of hydrogen bonding present.

As always, it gets more and more complicated the closer you look  (and of course there are exceptions to every rule)

[peadar1987]

Of course. My mistake. It's been a while since I did any chemistry. It was one of my favourite subjects in school though, so a little embarrassing that I don't remember my electronegativities!

[p1t1o]

1 minute ago, peadar1987 said:

Of course. My mistake. It's been a while since I did any chemistry. It was one of my favourite subjects in school though, so a little embarrassing that I don't remember my electronegativities!

Please. I use my chemistry training so little in everyday life that the other day I had to google what the-thing-that-is-a-unit-of-mass-that-hydrogen-has-a-value-of-1-of.

[K^2]

20 hours ago, p1t1o said:

Please. I use my chemistry training so little in everyday life that the other day I had to google what the-thing-that-is-a-unit-of-mass-that-hydrogen-has-a-value-of-1-of.

You mean a GeV?

Also, didn't they change definition of amu to something like 1/12th of ¹²C?

[p1t1o]

9 hours ago, K^2 said:

You mean a GeV?

Also, didn't they change definition of amu to something like 1/12th of ¹²C?

AMU yeah, and that is the correct definition (though 99 times out of 100 the integer value (H=1, C12=12, N=14 and so on) is correct to enough decimal places for most back-of-the-napkin sort of stuff).

I always get it confused with atomic number.

Edited October 8, 2016 by p1t1o

[Kobymaru]

How do people make these short Gifs of KSP gameplay?

What do you use for capture, what do you use for converting?

[K^2]

If you have a reasonably recent nVidia graphics card, try Shadowplay. It lets you record or stream your games with very little overhead. Most other solutions will hurt performance. Otherwise, my second recomendation would be Open Broadcast Software.

 

Once you have video, almost any video editor will be able to save GIFs. But if you just want a couple of short loops converted, there are online services that will do it for you.

The support for WebM is also growing, so you might want to consider it as alternative to GIF.

[Aghanim]

Some thought experiment of the day:

Lets say you are Jedi and you want to take a book across the room from your bed. You can walk, take the book and go back to your bed, or you can use the Force to telekinetically move the book to your bed. Because of law of conservation of energy, both of them requires more or less the same amount of energy, so do you prefer to walk or to use the Force, and why?

Edited October 16, 2016 by Aghanim
small rewording

[peadar1987]

1 hour ago, Aghanim said:

Some thought experiment of the day:

Lets say you are Jedi and you want to take a book across the room from your bed. You can walk, take the book and go back to your bed, or you can use the Force to telekinetically move the book to your bed. Because of law of conservation of energy, both of them requires more or less the same amount of energy, so do you prefer to walk or to use the Force, and why?

You use the force. The book has less mass than you, so it is less effort to move the book to you than to move yourself to the book and back to bed.

[p1t1o]

23 hours ago, Aghanim said:

Some thought experiment of the day:

Lets say you are Jedi and you want to take a book across the room from your bed. You can walk, take the book and go back to your bed, or you can use the Force to telekinetically move the book to your bed. Because of law of conservation of energy, both of them requires more or less the same amount of energy, so do you prefer to walk or to use the Force, and why?

The two tasks take different amounts of energy. When you walk over to get the book, you dont get the energy taken to move your body back on the return trip. Fetching it manually requires more energy.

Use the force to fetch the book, otherwise what use is it?

 

The force appears to be independent of energy conservation however.

[KayBee]

On 27/09/2016 at 9:35 PM, Toonu said:

I always wonder how fast is electricity?

Well electricity isnt a physical quantity which you can measure but its more of a phenomenon of flow of charge(or rather electrons). 

Now if you consider speed of electrons as speed of electricity it will be weird. Drift velocity of electrons in a wire carrying DC is less than one milimeter pre second! But electronic responses are fast because all the electrons in wire move simultaneously on application of potential difference(or voltage)

Its a common misconception that speed of electricity is very high. It cannot be calculated by like pumping water through a empty pipe and finding the time in which water reaches the other end BUT pumping water through a pipe already filled with water in which case water will come out of the other end almost instantly!

PS-sorry for bringing out an old question but in my defence it was not answered 

[Toonu]

2 hours ago, KayBee said:

Well electricity isnt a physical quantity which you can measure but its more of a phenomenon of flow of charge(or rather electrons). 

Now if you consider speed of electrons as speed of electricity it will be weird. Drift velocity of electrons in a wire carrying DC is less than one milimeter pre second! But electronic responses are fast because all the electrons in wire move simultaneously on application of potential difference(or voltage)

Its a common misconception that speed of electricity is very high. It cannot be calculated by like pumping water through a empty pipe and finding the time in which water reaches the other end BUT pumping water through a pipe already filled with water in which case water will come out of the other end almost instantly!

PS-sorry for bringing out an old question but in my defence it was not answered 

Ok, so it's almost always different? Like when we have 50km of high-voltage from power plant to something, you cannot measure it?

Anyway thx for another answer

[peadar1987]

On the water one, if you open a tap at the "upstream" end of the pipe, the flow will "react" at the speed of sound, which in water is about 1500m/s.

[DerekL1963]

1 hour ago, Toonu said:

Ok, so it's almost always different? Like when we have 50km of high-voltage from power plant to something, you cannot measure it?

It's different for different setups, but always the same for the same setup.  (And it can be measured with the right equipment...  I've done it myself.)

[JayPee]

What exactly is an "arguement of periapsis"? cant figure it out even after searching this forum/reading wikipedia

[K^2]

2 hours ago, JayPee said:

What exactly is an "arguement of periapsis"? cant figure it out even after searching this forum/reading wikipedia

It's the anomaly (angle) between ascending node (place where orbit crosses ecliptic or equivalent plane for parent body) and the periapsis, which is the lowest point in ship's/satellite's orbit. It is one of the six orbital elements that specify orbit and position of the craft. Basically, it's one of the things you need to know to define orientation of the orbit in 3-dimensional space.

[JayPee]

11 hours ago, K^2 said:

It's the anomaly (angle) between ascending node (place where orbit crosses ecliptic or equivalent plane for parent body) and the periapsis, which is the lowest point in ship's/satellite's orbit.

okay, thanks! that makes sense and is clearly understandable

[Green Baron]

A study suggests the hypothesis that, if bacteria can survive kilometers below the earth "feeding" on radioactivity, chances are they could as well under the surface of bodies in space, "feeding" on radiation.

I personally find this very far fetched. Noone can really confirm or reject this (right now) ....

[NoobTool]

Kinda spit-balling here, I've seen hybrid solid/liquid fuel rocket engines using a solid fuel and a liquid oxidizer, but what about using a liquid fuel and a solid oxidizer? This could conceivably allow for jet and rocket engines to use the same fuel on-board the same craft. Is there anything that immediately jumps out that would preclude the viability of such a set-up?

Edited October 21, 2016 by NoobTool