Conumdrum.

[Grumage]

Dear All.

I have attached a simple drawing of an idea of mine.

As we all know a strong magnet will induce eddy currents in the copper tube and slow the magnets decent. I found the mass of a magnet using a simple kitchen scale. I then placed a length of Copper tube on the scales and reset zero. I found that when dropping the magnet into the tube the scales measured the magnets mass as a force into the tube.

What do you think would be the outcome displayed by the device ?? 

Cheers Grum.

[ion]

Thank you Grum

My 2 cents:

The magnet will try to fall due to gravity, the induced current in the copper tube will resist, therefore the magnet will exert it's force directly on the tube and drag the tube along with the falling magnet since it is free to rotate on the axle.

Like a pendulum, the magnet and tube will be rotated to the nearly 9:00 position and then, then gravity will once again pull it back back nearly to the starting position. Each time it will lose some energy and this will continue until the oscillation damps out at the 6:00 position. There is not perfect coupling so there will be some slippage between tube and magnet.

You could replace the magnet with a steel ball  or marble and put a viscous fluid in the tube to simulate the Lenz coupling and get essentially the same effect.

[thx1138]

I was just going to say, gravity wins every time - it's relentless.

[Centraflow]

Hi Grum

Interesting thought, my 2 penny's worth

The tube has become a shorted coil!!! with induced current, which is different to just a straight tube which is not shorted, so I ask what will be the difference? an interesting thought which really needs the experiment done to be sure.

A bit like shorting the stator coil in Brads motor generator!!

regards

Mike

[forest]

I have an excersize for you    Measure weight of two identical magnets with hole in center then put one of them on the wood rod with round support at bottom (maybe glue that magnett to bottom) . Measure weight of this combination (magnet with rod + support) then add the second magnet in the way it will float in space above the first magnet.

Question : what is the weight of this whole assembly ?

[Verpies]

What do you think would be the outcome displayed by the device ?? 

From outside it will behave the same as if you'd filled out the tube with oil and substituted a marble for the permanent magnet.

[Grumage]

Dear All.

It's been more than a year since I opened this thread with Ion's single reply, then nothing. Now suddenly here we are.

I wonder still if the fluid analogy is fully correct? Wouldn't it depend on the viscosity? I also envisage two actions with a fluid the ball displacing the fluid around it, that fluid then exerting some force onto the tube wall. With a magnet that force is all exerted into the Copper tube.
From memory I'm sure I measured the total mass of the magnet was transferred into the tube, but it's been a while!

Sadly soft Copper tube is no longer used for domestic water service otherwise it would be quite easy to build a model and find out, one way or the other.

Dear forest, I have no idea what you're getting at, please post a simple sketch. I have not built anything but if I were to, it would be based around a bicycle wheel.

Cheers Grum.

Edit.

Having thought a little deeper about a fluid and a ball. Wouldn't the wheel want to move in the opposite direction to that of the ball? The fluid is being passed around it.

G.

[wattsup]

No. If the tube is on the pivot like in your drawing the whole thing will fall to 6 oclock and do nothing. End of story.

No conumdrum there. Gravity wins again.

wattsup

[Allcanadian]

I think if the magnet was falling in a copper tube on a scale it would weigh less than the static weight of the magnet and tube. If the magnet falls freely in a plastic tube the magnet has no measurable weight until it stops. Thus when the magnet's fall is resisted the amount it is resisted is added to the tube but not the full weight of the magnet until it comes to rest.

AC

[TinselKoala]

Almost right. As long as the magnet is _accelerating_ downwards the weight will be reduced, by the ratio between normal gravitational acceleration and the actual acceleration of the magnet. But when the magnet has reached "terminal velocity", which depends on the eddy currents in the tube walls, the weight of the combined tube + magnet will be the sum of their normal resting weights.

[Centraflow]

Am I the only one who sees this as a shorted coil?  Grum's drawing is just that and not a straight tube!!!!!!!!!!!!!!!!!!! The question was :- What do you think would be the outcome "displayed by the device"

Regards

Mike

[TinMan]

Am I the only one who sees this as a shorted coil?  Grum's drawing is just that and not a straight tube!!!!!!!!!!!!!!!!!!! The question was :- What do you think would be the outcome "displayed by the device"

Regards

Mike

A straight piece of tube it self is a shorted coil. As the shorted coil effect(eddy currents pushing against the magnets direction of travel)is local to the magnet passing through it,then i dont see what difference a full loop would make. In fact,a flat sheet of ali or copper held near a spinning rotor that has PM's in it,will cause a load on that rotor. So it dose not even have to be a loop(as in a pipe). If you take a sheet of copper,and angle it as say 80*,and then place a PM on that sheet so as it slides down,it will experience the same eddy current drag.

I seem to remember TK (i think?) doing something like this. But i think he would place the magnet one way,and it would slide down slowly,but when he turned the magnet around,it slid down quickly. I cant quite remember the detail's,and i may have that wrong,but i remember something odd with the test.

[Centraflow]

Hi Brad, I really don't see why a straight tube of copper is the same as a circle of copper "or any other metal". It is simply open ended or looped, looped in this case is a shorted coil, yes or no!!!! one turn closed or 1000 turns closed, it is the same, a shorted loop or not??

regards

Mike

PS I'm not getting uptight, just a little bemused, can't anyone see this?