Questions tagged [perpetual-motion]

Perpetual motion describes "Motion that continues indefinitely without any external source of energy; impossible in practice because of friction." It can also be described as "the motion of a hypothetical machine which, once activated, would run forever unless subject to an external force or to wear". There is a scientific consensus that perpetual motion in an isolated system would violate the first and/or the second law of thermodynamics.

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Would it be possible to create a perpetual motion machine in an environment without air, friction, or dissipation?

Perpetual motion machines don't work because as it moves, the air molecules hit it and slow it down. Friction slows it down in a similar way. If there were no forces to slow it down, could it work?
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Perpetual motion machine with permanent magnets [duplicate]

I am not a physicist, but I know the first law of thermodynamic (conversation of energy), and I have connected this with an idea that came to my mind some time ago to create perpetual motion machine ...
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Perpetual machine from a PN-junction diode [duplicate]

Consider a PN junction diode Now, this system will naturally form a depletion region due to diffusion and will convert into this- Now, I wish to connect the ends of this diode with a conducting wire ...
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Feynman Lectures, Chapter 4, Fig 4-2

Chapter 4 of the Feynman Lectures Feynman defines the following: We imagine that there are two classes of machines, those that are not reversible, which includes all real machines, and those that are ...
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Eternal looping water tap

If i have a container like this (filled full with water): and I unplugged the small tap, would the water pressure be big enough to blast the water to the right side of the container and cause an ...
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What prevents a (theoretically ideal) railgun from being a perpetual motion device?

So, I understand the basics of how a railgun works - the current in the conducting rails and the armature sets up a magnetic field, which, via the Lorentz force acting on the current in the armature ...
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Buoyancy perpetual motion machine with compressors at top and decompress-or at bottom [closed]

a link to consideration about the perpetual motion machine [] diagrams and working out are included above. the assumptions are set to minimise engineering challenge and face perpetual motion machine ...
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'Perpetual motion' paper by George Biddell Airy

Airy wrote a paper (maybe deceptively) titled On certain Conditions under which a Perpetual Motion is possible (Cambridge Philosophical Transactions, December 14, 1829). Alternative site (in more than ...
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Perpetual Motions in atoms up scaled to Tesla

If perpetual motion exists in atoms or its parts then why can it not exist with a collection of atoms? or can it? What exactly prohibits or where does the perpetual line physically stop? Can atoms be ...
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Voltage drops in series - less work to do the same job

So I have been trying to explain electricity to younger siblings and it surprised me how little I know of what actually goes on. My question comes in the form of a consideration: Consider a ...
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A question about infinite energy

I know the conservation of energy doesn't allow that, and i saw a question on this forum about infinite energy: Why can't I do this to get infinite energy?, it says we can convert matter into ...
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Would electrons flow around the loop continuously in the following diagram

If there is a plate that is negatively charged (like the negatively charged plate of a capacitor) and it is brought near to (but not touching) a copper wire loop with a light bulb (load) and a diode (...
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The “free” energy device is possible if you look like this? [closed]

As I understood (please correct me if I am wrong) all “free energy” devices, in the end, stuck on the “energy conservation” law so you can’t have more energy than you put into the system. But I think ...
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A confusion about the impossibility of perpetual motion

It is stated that If any engine could produce a greater amount of work than that produced by a reversible cyclic heat engine, then it was possible to produce work endlessly by the following ...
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Do MRI scans take energy from the electro-magnet?

I read that a MRI machine generates a powerful magnetic field produced by an electric current. In order to get a high current (and a strong magnetic field) without too much heat as a side effect, ...
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Why would this evaporation-based perpetual motion machine not work?

This morning I was struck by an odd thought: Hydroelectric power stations get energy by dropping water from a height. The greater the height difference between top and bottom, the more energy can be ...
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Feynman's Reversible Machine Argument

In Feynman's Lectures on Physics, in the lecture on the conservation of energy, he makes the following argument: Consider weight-lifting machines—machines which have the property that they lift one ...
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Is “Air-gen” really possible, and how is it different from perpetual motion?

"Air-gen", as seen in Nature (See here and here), supposedly extracts net positive energy from ambient air at equilibrium. Is this really possible? Doesn't this violate a law of thermodynamics ...
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Would a room temperature superconductor break the laws of thermal dynamics? [duplicate]

I know that is roundabout way ask a question about perpetual motion but if I mentioned that in the title. No one would read it 😁 I guess I really need some help with my paradoxical thought. So here ...
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How do electrical motors obey the conservation of energy?

Feynman introduces the concept of an electromagnetic motor with this diagram. I believe I understand why the wire turns when there is current through it, because $F = q(\mathbf{E} + \mathbf{v} \times ...
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A hypothesis for obtaining energy from gravity in conjunction with time [closed]

Have a scenario which appears to be a contradiction to the established laws with regard to conservation of energy. It goes as follows - If a mass of 2 kg is dropped from a ceiling (height) of 100 ...
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Why are perpetual motion machines impossible?

Is the reason we don't have any perpetual motion machines because of the first law of thermodynamics? Would it be possible to create one if (for example) there was a wheel, and it had a push– if it ...
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Perpetual Motion Explanation [duplicate]

Hello could someone explain the reason why this machine does not work. There is an explanation in the text but I cannot seem to follow it. Here is the link - it's the buoyant spheres perpetual motion ...
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I want to know more about this specific perpetuum mobile [duplicate]

Sorry for beeing another noob asking stupid questions, but I just wanna know more about this specific perpetuum mobile. What prevents this magnetic perpetuum mobile from working? I don t say I full ...
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A simple though experiment: molecular sieve + buoyancy = perpetual motion?

The picture below is a low-effort mock-up I made showing a closed loop with uniform ambient room temperature and top-down gravity containing two species of gas—although the idea may apply equally to ...
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Perpetual motion of zeroth kind?

Perpetual motions are classified by which law it breaks: Perpetual motion of first kind breaks the first law of TD. It generates energy from nowhere. Perpetual motion of second kind breaks the second ...
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Naive question - Is Magnetic generator (like this) not a 'perpetual motion machine'? [duplicate]

Perhaps a question that is too naive to be on Physics.SE but I let the experts here decide (and downvote at will), but there seem to a certain company that claims to have created what it calls a "...
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Searl effect: myth or reality? [closed]

Recently I heard about Searl effect. Allegedly, this generator produces "free" energy, and that John Searl was accused of stealing electricity, but in fact he provided the entire laboratory with ...
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Impossibility of perpetual motion as a mathematical theorem

Can the impossibility of perpetual motion be expressed as a mathematical theorem?
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Infinite Electricity from Photon Inside Closed Box with Magnet Attached in a Coil? (Thought-experiment)

Let's say I have a very large box with a magnet attached to the outside. Inside the box there is a perfect mirror on each side. I open my box and quickly shoot in one photon before shutting it. After ...
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Perpetual magnetic attraction

There are two magnets, M1 and M2. Let's say that there is an attractive force existing between M1 and M2. M1 is attached to a surface, while M2 is free to move. Now slow this motion down, and M1 is in ...
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Perpetual Motion Machine 1: Magnetic Superconductor Loop Generating Energy with Piezoelectrics [closed]

I know there are a lot of perpetual motion machine designs out there, but I haven't found one that looks like this one. I will use this diagram. Assume the entire ring is made of a superconducting "...
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Energy balance of this machine is positive. What is wrong? [duplicate]

Machine on this picture is inspired by video: https://www.youtube.com/watch?v=rxFXsoqbfrk There must be error in the computation of energy balance or there is another negative energy. Can you help ...
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Can we use the power of ice to float to make free electricity?

ice and water have a volume to weight ratio of 12/11 so 11 tons of ice will support 1 ton of weight 1 ton of ice takes 1000 watts or 12000 b.t.u. of energy to be produced question is, at what depth ...
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Why can't we make a perpetual motion machine by using a magnet to pull up a piece of metal, then letting it fall back down? [duplicate]

Obviously, a perpetuum mobile isn't possible by any law in physics, because energy can't be "created" or "destroyed", only transformed. This said, I've had an idea for a perpetuum mobile and can't ...
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Can we use the stored gravitational potential energy of a building to produce power? [closed]

There are skyscrapers sitting and pushing on the ground with tremendous weight. Is it possible to convert this weight/force to harness energy to power the building? Maybe build the building on top ...
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Harnessing molecule vibration energy

Disclaimer: I am learning physics for fun, please dont kill me but explain where I am wrong. As I understand all molecules have a lowest energy state in which they posses some amount of momentum even ...
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Is there an upper limit on entropy density?

I would like to sell you a perpetual motion machine that works by making the insides of a box continually more messy. The engine comes packaged with a physicist who will continually discover new ...
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Perpetual Motion and Thermodynamics [duplicate]

How does the second law of thermodynamics disprove all perpetual motion machines?
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Doesn't expansion of space not allow a perputual motion?

Well consider the following thought experiment: We have a tool to extract/transform "nearly all" potential gravitational energy into other forms of energy. We can theoretically make such an object (...
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Perpetual motion using mass defect

First off, I know this wouldn't work due to it breaking thermodynamics and that there would also be heaps of energy dissipated to the surroundings, and fusion doesn't work yet, but I'm more interested ...
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Is mass-energy conversion contradicting energy conservation? [duplicate]

If mass can be transformed into energy, and energy transformed back into mass, isn't this at odds with the law of conservation of energy? Because this would mean, that in theory, it would be possible ...
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Derivation of 2nd law of Thermodynamics from ergodicity assumption

In Wikipedia it is claimed that: Assumption of the ergodic hypothesis allows proof that certain types of perpetual motion machines of the second kind are impossible. Since perpetual motion ...
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Is it possible to create a limitless power by firing rocks from the moon to Earth? [closed]

Here is my idea for a limitless* power. A gun on the moon fires moon rocks towards the Earth. The moon rocks fall in Earths gravity picking up speed and smash into Earth's atmosphere generating huge ...
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Does a heat engine inside of a refrigerator increase efficiency?

Consider a normal refrigeration cycle, except a heat engine runs off of the temperature difference between the evaporator and the condenser, as shown below. This heat engine powers the compressor, so ...
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Is self-perpetual system possible?

As I was reading a intermediate part-2 book I come to know that self-perpetual system is not possible. So i wanted to know if it is possible or it's completely impossible.
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auto-refilled nuclear fusion generator [closed]

I read in a science article that in a nuclear fusion reactor, the energy we bring to the reaction is multiplied by a coefficient q. This coefficient needs to be at a certain level (around 7 if my ...
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If there were no inertia would perpetual motion be possible? [closed]

Is it not inertia that makes a flywheel resist being put into motion? And if that is true, is inertia a consequence of being unable to create energy, i.e., why perpetual motion machines do not in fact ...
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Is it possible to generate conditions such that the temperature difference created by current is high enough to sustain it?

We know that current can generate temperature difference and vice-versa. But is it possible to generate such conditions that the temperature difference created by current is high enough to sustain it?...
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Can Bhaskara's Wheel increase the efficiency of wind mills?

Bhaskara's wheel is an ancient attempt at perpetual motion. The idea is that gravity will pull the water toward the center for the bottles at the top and toward the ends for the bottles falling to ...

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