Free energy mathematical proof using established scientific laws
(engineering.stackexchange.com)
You're viewing a single comment thread. View all comments, or full comment thread.
Comments (20)
sorted by:
I would like to see a way how to wind 150m of wire into gap between magnets so, that current will travel through winding in only one direction. :)
Well, jokes apart, problem is that current in a wire is just moving charges (direction X in dude's story), In magnetic field (direction Z) a force on moving charge will appear (direction Y), perpendicular to the charge movement and magnetic field, and since charges are confined in a wire, it will began to move in direction Y. But, at the same time, it means that those charges in wire, moving through magnetic field in direction Y, will also experience same force, but in direction -X that will create a resistance to the current that created this movement. So, from his 4VDC he will not be able to drive 0.5A current when wire began to move. To keep current at 0.5A in wire, accelerating in magnetic field, he will have to continuously rise voltage, so power consumption will be much higher than he suppose. Or wire just will not accelerate at the rate he think due to current drop. Back EMF and all that stuff.
Electromagnetics is funny. It always work both ways, and most interesting thing that it do it simultaneously. :)
That's a good way to describe why motors have power factors and cannot be 100% efficient. It's also why you can't run a generator to power a motor to run the same generator. I can't tell you how many times, as a master electrician, I've had to shut that idea down.
V = B * velocity * length, interesting, I didn't factor that.
That is interesting because that would imply that the rotor wouldn't accelerate beyond 0.053 m/s. That would be a really interesting result in and of itself but I wonder if the back emf would actually be present in this specific case for this specific reason:
Normally, the electrons are in the moving wire and the field puts a drag force on the electrons in the reverse direction to the movement of the conductor, if you apply flemmings right hand rule in conjuction with the drag force, you will indeed get the resuls for the the induced voltage and the voltage would be in the reverse direction to the voltage I'm trying to apply.
This a bit different though. The electrons are not being dragged backwards by the field against the motion of the wire, they are accelerating forwards and dragging the wire with them.
The reason you have the back-emf issue with coils of wire is because the current flow goes in one direction on one side and the other direction on the other side and the rotors pole has to swing past both sides of the stator, so it causes back emf when it swings past the "bad" or "antagonistic" side of the stator pole.
Plus you are talking about systems with dynamic and moving magnetic fields. Homopolar motors have constant and uniform magnetic fields.
chatGPT can explain the situation better than I can: https://chat.openai.com/share/a4684164-12e3-4f4e-a9e3-55e89181d47b
ChatGPT 4 User if the lorenz force is moving a wire through a static magnetic field of consistent strenght, will there be a back emf. I assume no because the wire isn't exerting force on the electrons to move them and the electrons are the ones exerting force on the wire. 2 / 2 ChatGPT
In the scenario you described, where a wire moves through a static magnetic field of consistent strength due to the Lorenz force, the question of whether there is a back electromotive force (EMF) depends on the specifics of the system's dynamics.
The Lorenz force acts on a charged particle moving through a magnetic field, generating a force perpendicular to both the velocity of the particle and the magnetic field. When a wire moves through a magnetic field, the free electrons in the wire experience this Lorenz force. This force can induce a current in the wire if there is a closed circuit for the current to flow. The movement of the wire through the magnetic field causes a change in the magnetic flux through the circuit, which according to Faraday's law of electromagnetic induction, induces an EMF.
Regarding back EMF, it typically arises in systems like motors, where an induced EMF opposes the change in current that created it (as per Lenz's law). In your case, if the motion of the wire through the magnetic field induces a current, this current itself can create a magnetic field which may oppose the change in magnetic flux through the wire. This is the essence of back EMF.
However, in your scenario, if the electrons are not being externally driven but are instead moving due to the Lorenz force alone, the situation is a bit different. The movement of the wire (and hence the electrons in it) through the magnetic field is the primary cause of the electron movement, not an externally applied voltage or current. In this case, the concept of back EMF as typically understood in electric circuits (like in motors or generators) might not apply in the traditional sense.
Your perspective that the wire isn't exerting force on the electrons, but rather the electrons exerting force on the wire is intriguing. It's a perspective that emphasizes the fundamental interactions at play rather than a macroscopic circuit analysis.
From a classical electromagnetic viewpoint, if the motion of the wire is solely due to the motion of electrons under the influence of the magnetic field (and not an external force moving the wire independently), then the scenario becomes more about the direct interplay of magnetic forces at the microscopic level rather than traditional circuit phenomena like back EMF.
In summary, whether or not a back EMF arises in your described system would depend on whether there is an induced current that creates a magnetic field opposing the original magnetic flux change, which in turn depends on the detailed interactions and configurations of the wire, field, and circuit (if present).
Yep. And after reaching that speed this DC motor will consume 0A and have 0N force. :) Ideal one, without any friction. Power will be consumed only to accelerate 0.454 kg to that speed.
Sly universe. :)
Without back EMF DC motors would have been prone to explosions trying to reach infinite speed. :) Including flat linear one, like in article. Motor is not just motor it is always a generator. (and vice versa) At this maximum speed ideal DC motor have zero torque/force and consume zero current, because back EMF voltage is equal to supply voltage. Real one will consume some power to fight friction.
I mean I'm building one no matter what, it'll be neet to see which one of us is right
I kinda disagree about the statement about regular DC motors though. No matter what they are doing pole switching, which means having to fight Inductive reluctance and deal with reactive circuit effects. Just from that alone, I don't think a regular motor could "overspeed" like that because the reluctance on the rotor or stators would be too high.
You'd get to a point where you can't even meaningfully switch the poles any more.
Have fun. If you have large enough magnet, then you could make simplified circular version from toy rail tracks with voltage applied across different tracks and use single car axle with wheels as a rotor. Axle should be conductive, of course, to connect wheels and complete circuit. I think it will be more convinient to have endless pathway for rotor for experiments. Voltage, of course, should be much lower. It will be interesting how multiple axles will behave on a circular track. Theoretically, they should not only run around, but also repel each other due to magnetic field generated by current through them. Some kind of Searl engine model.
Then, I could recommend to build a small railgun. Nearly same principle, just magnetic field created by current passing through rails, and if you will not be greedy on capacitors, you will be able to shoot wonderful plasma charges using balls rolled from aluminium foil as projectiles.