# Laws of thermodynamics [closed]

Does it violates law's of thermodynamics if it's using ambient field or energy to move?

Perpetual motion devices are seen as witches in middle age, because every time somebody mentions, there's a huh 'thermodynamics' comment.

Problem is that those devices can harvest energy from sources like gravity, and therefore they don't violate anything.

I can state three kinds of perpetual motion mechanics, but I don't have money for patent, all is working in mathematics, doing conversions and stuff like that.

Is there some punishment for violating Newton's Law's, or why don't we use gravity or heat in sea water or air to get energy? It does violate nothing! Most people just think too much in a box.

Does it violates law's of thermodynamics if it's using ambient field or energy to move?

Yes. Because it assumes the energy source is infinite. No “ambient field” is an unlimited energy source. In order to run indefinitely it would have to run without energy input thereby violating the first law of thermodynamics (conservation of energy).

Problem is that those devices can harvest energy from sources like gravity, and therefore they don't violate anything

Yes they do. Gravity is not an unlimited energy source. In fact it is not an energy source at all. It’s a force that can convert potential energy into kinetic energy and vice versa. Some external energy source is needed for an object to obtain gravitational potential energy- like you lifting an object.

why don't we use gravity or heat in sea water or air to get energy? It does violate nothing!

I already addressed gravity. Regarding air or the sea, neither is an unlimited source of energy since both get their energy from the sun and the sun will eventually die as an energy source. Remember a perpetual motion machine is defined as one that runs forever. So it again violates the first law. This type of motion is also classified as perpetual motion of the second kind. A perpetual motion machine of the second kind is a machine which spontaneously converts thermal energy into mechanical work. This violates the second law which says a heat engine operating in a cycle cannot produce net work exchanging heat with a single thermal reservoir. Some heat must be rejected to a lower temperature reservoir.

Hope this helps.

• Okey, it's like I can still smoke crack because cannabis is illegal, but I like it. Ambient means in space around you. Like heat in water or air, just compress air, power heat engine and power compressor by the heat engine, it works. And when it comes to gravity, you can lift object using lever so going down gives you more potential energy than going up if you switch what is on what distance of the lever. It's just 3D shape nothing more. May 29, 2019 at 12:18
• @JurajDobrik I have no idea what you are talking about May 29, 2019 at 12:47

Throughout history all sorts of perpetual motion devices have been tried, some of them have been incredibly creative. However, they always violate at least one of the laws of thermodynamics, let me explain.

First, a machine can only output (at maximum) the amount of energy that you put into it. This means that there is no "free energy" device, because energy cannot appear from nowhere. To avoid this, some people claim that their invention instead harvests some previously untouched sources of energy, like gravity, the magnetic field from earth, etc.

I don't know which device you may be referring to, so I will explain some of the common problems.

Let's begin with the ones that utilize gravity. Remember that the force of gravity is what we call a "conservative force". This means that the net work done on a closed loop is zero. So if you have a spinning wheel, for example, and it has some system so that it redistributes its weight to "keep spinning indefinitively", you cannot harvest energy from it! Because in a perfect world it would keep spinning forever (no friction), but every bit of energy you took out would slow it down until it stops. And in the real world, it would stop by itself.

Also, some of those devices shift the wheel's axis of inertia, and as you might have seen in rigid dynamics, that means that there will be loss of energy during the rotation. So spinning wheels due to gravity don't work. But what about other sources, such as magnetic or electrical fields? After all, there is not only earths magnetic field, but also a lot of fields generated by us, with energy that is wasted! Could we "recycle it"?

Here the problem is that a magnetic field does NOT generate energy by itself. Rather, a CHANGE in magnetic field does. And the problem is that the magnetic field is static relative to us, so in order to harvest power from it you would have to move the coil through the atmosphere relatively fast, which would consume more energy than you could take out.

As for radio signals and waves that are in the air, the power is way too small to be useful, as they are only a fraction of the power that was used to emit them.

If you want further explanations, I can recommend two good sources. 1-"Why don't perpetual motions ever work?" by Ted-ED

2- An electrical engineer has a channel called "Electroboom", where he adresses Fre energy devices and explains why they don't work. He has several videos about it, which I highly recommend. You can start with "The boy who cried Free Energy"

• Only if you use lever to put counterweight to a position with greater potential energy. May 29, 2019 at 6:58

Ist Law of Thermodynamics: Matter & Energy Can Neither be Created nor Destroyed. You can't create energy from nothing,you can only harvest energy which is already there. Another thing to remember is that no machine is 100% efficient; there is always energy wasted due to friction & other losses. There is a hydroelectric generator in N.Wales which harvests the gravitational energy from a lake at the top of a mountain as it drops to another lake at the base,but this is not perpetual motion harvesting energy from the Earths gravitational field. When a substantial quantity of the water at the top has been used up,it has to be replaced by water pumped back up from the bottom in off-peak hours. Some water is replaced by rainfall,so to that extent it is free,but it is not perpetual motion. The energy used to pump the water uphill is less than the energy generated when it is allowed to fall back down again. As for the rainfall,solar energy is required to send it to the top of the mountain. Solar energy is a kind of perpetual motion,because from a human perspective there is an endless supply of it which we can go on harvesting for as long as the human race exists.

• It can by only converted, why don't we convert heat in air? May 29, 2019 at 6:57

why don't we use gravity or heat in sea water or air to get energy ?

Perpetual machines is biggest buzzword in the planet, however thousands of their prototypes was denied by physicists in the past and WILL BE in the future. Holy Grail or free lunch exists only in movies.

However the most real of your suggestions is heat extraction from the sea. It can be done and there's nothing new in such type of projects. See Thermoelectric generator or Solar thermal collector. But :

1. It's not a perpetual machine, because uses sun's light energy indirectly
2. Problem with these types of projects is that they generates very small amount of electricity. If you want bigger amounts of output energy - you need to use thermal collectors with very big surface area. And this becomes a problem for a collector manufacturers - hard to make these and they become fragile and hard to maintain. Unless you build an collector arrays.

Now with a sea heat - it's much more problems here. You will need a big collector array in sea, meaning that they will block sunlight to the creatures living below in water, so you will change sea ecosystem to the bad course of things. And you can't move this collector array deeply because sea temperature will drop drastically deep below surface to the point you will get no useful energy out of if.

Second, when extracting heat energy from the sea water - you'll probably change sea underwater currents which will affect sea ecosystem and creatures to the bad side too.

Third. Probably you don't want to use sea heat for turning on some light bulbs ? Maybe you are thinking about large scale experiment such as some type of thermal power plant to feed electricity to New York of maybe to whole planet. Then think about issue - what will be if electricity consumption will be so big, that there will be not enough heat from a sea ? To extract even more heat, you will need to cool-down heat collector even more. And you understand that for cooling collector you also need an energy ?