Can a Magnet-Driven Tube on the Moon Function Perpetually?

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SUMMARY

The discussion centers on the feasibility of a magnet-driven tube on the Moon functioning perpetually. Participants conclude that while a magnet dropped in a vacuum tube may oscillate, it cannot generate perpetual motion due to fundamental principles of physics, specifically Lenz's Law and Faraday's Law of Electromagnetic Induction. The opposing magnetic fields generated during the motion of the magnet through a solenoid create resistance, preventing continuous energy generation. Additionally, even in an ideal scenario, energy losses due to various factors, including the weight of the object and atmospheric conditions on the Moon, would ultimately dampen the system.

PREREQUISITES
  • Understanding of Lenz's Law and Faraday's Law of Electromagnetic Induction
  • Basic knowledge of magnetic fields and their interactions with electric currents
  • Familiarity with the concept of energy conservation in mechanical systems
  • Awareness of the effects of friction and resistance in electrical systems
NEXT STEPS
  • Research the principles of Lenz's Law and its implications in electromagnetic systems
  • Study Faraday's Law of Electromagnetic Induction and its applications in generators
  • Explore the effects of weight and resistance on energy systems, particularly in gravitational fields
  • Investigate practical demonstrations of magnetic fields and induced currents, such as the magnet drop experiment
USEFUL FOR

Engineers, physicists, and hobbyists interested in electromagnetism, energy generation, and the principles of motion in gravitational fields will benefit from this discussion.

Dumb Idea
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... with all this drilling equipment and an idea, albeit a dumb one.

Big tube, through the moon. Big permanent mag lev tube... packed with solenoids... and a brick, covered in magnets.

Drop the brick in the tube, vacuum of space, no resistance that I can think of...

Hooke says it will oscillate back and forth forever.

Why won't it?
 
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Why do you think you need a solenoid and magnets, it will oscillate with gravity alone...


Would be best if your hole was on the axis of rotation.
 
Because dropping a magnet through a solenoid creates electricity... which would violate conservation... so why won't it work?
 
Dumb Idea said:
so why won't it work?
The same reason that you can't just start a generator spinning like a top and generate free energy forever.
 
Friction is why you can't do that.

Why can't you do it in the above scenario?
 
Assume an ideal generator with no frictional or heat losses. The generator would still not spin forever generating power.

Do you know how a generator works? In a typical well-designed generator the friction losses are negligible. I would start with the http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html" .
 
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Evidently I don't know how GOOD generators work.It requires energy to generate that electricity... through whatever processes that allow efficient motors to operate, it cannot breach 0 point.Gravity is not electricity, or energy even I don't think... it is nothing without mass. It is a force... it is a constant force... which is a source of potential energy.

I guess what you are saying is that the conversion of that potential energy TO energy will result in something "magic" that prevents it from continuing to do so.

I am asking, specifically, what will occur that prevents gravity from having it's effect, or from permanent magnets from having their effect, or from Faraday's law what keeps the coils from energizing. "It doesn't work that way" is NOT what I am asking for. What specifically will keep THAT from working? There is no electricity being used, only generated. There is no "energy" being used, just potential energy being converted... as near as I can see.

I prefaced this with the fact that I am an idiot. I just need to know why. I can't sleep. It has been almost a week now. Please help me sleep.
 
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I am thinking it has something to do with Lenz, but being an idiot with only most of a public school education about a millennium ago, I don't understand Lenz, or Faraday, so I make that claim with no understanding whatsoever. I just believe it.
 
A generator converts mechanical kinetic energy to electromagnetic energy. It is electromagnetic forces that oppose the spinning of the generator and the motion of your device on the moon.
 
  • #10
Dumb Idea said:
Evidently I don't know how GOOD generators work.
Oops, I didn't test my link and the hyperphysics one did not work. Please read the HyperPhysics pages on:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magint.html#c1"
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/forwir.html#c1"
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/motdc.html#c1"
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/mothow.html#c1"

A motor is just a generator run in reverse. If you still have questions on how they work, then please post a follow-up and I will be glad to help. The bottom-line is that magnetic fields exert forces on currents. In generators those forces oppose the external force such that the external force does mechanical work to produce electrical energy.
 
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  • #11
In order to generate electricity you will have to have a magnet moving through a magnetic field. The magnetic field will exert a force on the magnet, eventually slowing to a stop. That's why such a "perpetual motion machine", even under ideal circumstances, cannot work.

In practice, there is a slight amount of atmosphere on the moon so even without trying to draw energy out of this, it would eventually stop. But the answer to your question is that in order to generate energy, you must have some kind of resistance.
 
  • #12
So... as the magnet passes through the center of a solenoid, the magnetic field changes direction? Is that where the resistance comes from? Is there a way to calculate that resistance?

Also, does the velocity of the magnet have any effect on the amount of electricity generated?

I suppose using electromagnets on one end to pump it back up to the top would use more electricity than it generated eh?

Lastly, would the weight of the object have any effect? It seems to take more energy to get something heavier off the ground (like a loaded airplane vs an empty one requires more energy, with the same resistance) while it will be drawn towards the center of gravity at the same speed (the pound of feathers pound of lead in a vacuum thing).

I really appreciate all of your help thus far. My wife will too now that I will abandon this concept. I wanted to build a 3000 mile pipe that rested on the continents and on the ocean floor. 42 minute trips across 3000 miles seemed like a lot of juice.
 
  • #13
Dumb Idea said:
So... as the magnet passes through the center of a solenoid, the magnetic field changes direction? Is that where the resistance comes from? Is there a way to calculate that resistance?
What happens is that as the magnet passes through the coil, it induces a current in the coil (This is the electricity you hope to tap). When this happens, the coil itself becomes an electromagnet, and the polarity of that electromagnet will be such that its magnetic field will oppose the motion of the magnet.

To calculate the retarding force you would need to know the strength of the magnet, the parameters of the coil and the load on the coil.

Also, does the velocity of the magnet have any effect on the amount of electricity generated?
Yes, and it also effects the resistance to the movement of the coil. If you've ever experimented with a hand cranked generator, you will notice that, under load, it becomes harder to crank the faster you try to crank it
I suppose using electromagnets on one end to pump it back up to the top would use more electricity than it generated eh?
most definitely
Lastly, would the weight of the object have any effect? It seems to take more energy to get something heavier off the ground (like a loaded airplane vs an empty one requires more energy, with the same resistance) while it will be drawn towards the center of gravity at the same speed (the pound of feathers pound of lead in a vacuum thing).
The weight of the object will determine how quickly the system will damp out and how much energy you can get from it before it completely damps out.
I really appreciate all of your help thus far. My wife will too now that I will abandon this concept. I wanted to build a 3000 mile pipe that rested on the continents and on the ocean floor. 42 minute trips across 3000 miles seemed like a lot of juice.
 
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  • #14
There is a neat little demo I saw in high school, where the teacher drops a magnet down a pipe and the magnet slowly makes its way down the pipe due to the current it induces in the pipe and the accompanying resistance to its ability to fall. It is precisely what you are trying to do.

http://www.coolmagnetman.com/magpipes.htm
 

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