Thread: Please help find flaw of following perpetual motion machine

There is a magnetic field pointed to one direction as depicted in upper image in black arrow line. There's smooth track in red color, part of this track is in the magnetic field, the track outside magnetic filed using line to represent. Also there's smooth iron ball in the track. As iron ball moving toward the direction of the strength-intensive magnetic field, once it leaves the magnetic filed, it has a kinetic energy, so it will go back to the starting point, as the track outside magnetic field is smooth, seems the kinetic enerty is increasing. Who can help to find flaws in this machine, thanks a lot!
Magnetic filed can be generated via horseshoe magnet as depicted at the bottom of the image

It would work if one can make a field like that. One can't.

It wouldn't even work if you could make a field like that. In reality, there won't be an abrupt end of the field, but for simplicity, let's assume there is.

Now, to extract the ball from the field will require exactly as much energy as it gained (or less if you include friction or hysteresis), so it would leave the field with exactly the same or a lower speed than it entered.

The magnetic field lines for any magnetic field are never straight lines. They look more like this:





They're always like this. There's no way to change it. In fact, the way magnetism is created guarantees that the field lines will always be curved no matter what you do. Trying to use multiple magnets together, or other approaches like that probably wouldn't give you the effect you want... but maybe.

Energy cannot be created or destroyed it only transforms from one form to another.

The Neanderthals figured this out, by following rivers downstream, skipping stones, and lighting fires.

Originally Posted by kojax

The magnetic field lines for any magnetic field are never straight lines. They look more like this:

They're always like this. There's no way to change it. In fact, the way magnetism is created guarantees that the field lines will always be curved no matter what you do. Trying to use multiple magnets together, or other approaches like that probably wouldn't give you the effect you want... but maybe.

Magnetic fields aren't used like in these images. You want to keep the airgap small, and if you do that, the field lines in the air gap can be approximated quite well by straight lines. If you guide the magnetic field through a long, tin iron core, they'll also be mostly straight.

In fact, in the left image, there will be one perfectly straight line going up and down, the right image doesn't represent the field lines very well, and there will be nearly straight lines going from left to right inside the U.

But to get fieldlines close to what he wants, Marshroom should use an electromagnet and not permanent magnets.

Originally Posted by Bender

But to get fieldlines close to what he wants, Marshroom should use an electromagnet and not permanent magnets.

If it's an electromagnet, then he's already using energy just to create the magnetism.

I suspect that during Magnetization, iron material can absorb energy from space, please check the follwoing model


There's magnetic field in the horizontal direction, assume 2 iron bars are smooth, when they moving into the filed, 2 iron bars will be magnetized and release energy, because the filed is uniform filed, each iron bar won't be attracted by it. so when pull 2 iron bars out of the filed, the 2 iron bars will loose magnetic. Assume there's no friction. Also some one may think that the magetic of horizontal filed will reduce, but if we put it in the same direction with the geomagnetic.

Then can we think that magnetization is the process of absorption of energy from space?

I don't know what you are trying to say.
There is magnetic energy, and depending on the source, the total magnetic energy will decrease when the iron enters the magnetic field (in case of an electromagnet, the total magnetic energy will increase, but not as much as the added energy by the electromagnet).
The field will no longer be uniform but concentrate through the iron bars. The magnetic energy in the bars will increase, but in the air around it, it will decrease.

If the iron bars are removed, the distribution of magnetic energy will revert to its previous state (if the iron is pure and the remanent field is negligible).

Originally Posted by kojax

If it's an electromagnet, then he's already using energy just to create the magnetism.

Yes, but we were already neglecting friction, so why not neglect electrical resistance. The coil would use energy when magnetic material is inserted, but get it back when the material is removed.