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Author Topic: Measuring Amps on output coils  (Read 27376 times)

Low-Q

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Re: Measuring Amps on output coils
« Reply #15 on: March 22, 2015, 12:31:41 PM »
Current flow has everything to do with voltage. If you have no potential difference,then current will not flow. The voltage differential may be very small,but there has to be one. I must also ask how current flows in ferrite magnet's,as the ferrite is non conductive,and even if it were,you would have nothing but a dead short. A dead short with current flowing through it means extensive heat-->PMs do not get hot sitting on the bench.
You're right if you consider the energy source as the voltage drop. The voltage drop over the super conductor is zero, but current is still flowing.
Inducing current flow through a super conductor using a passing magnet, there is no voltage present anywhere but the current is flowing still.


The point is that Ampere or Voltage alone cannot be considered as energy. Only the product of them are energy.


Vidar

tinman

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Re: Measuring Amps on output coils
« Reply #16 on: March 22, 2015, 02:21:14 PM »
You're right if you consider the energy source as the voltage drop. The voltage drop over the super conductor is zero, but current is still flowing.


The point is that Ampere or Voltage alone cannot be considered as energy. Only the product of them are energy.


Vidar
Quote
Inducing current flow through a super conductor using a passing magnet, there is no voltage present anywhere but the current is flowing still.
Where is it flowing?. In order to have a flow,it must have direction. So in a super conductor,which direction is this flow of current?. The same question would apply to the PM. We often use waterand pipes to explain current flow through a wire. Is a super conductor represented by a bucket full of water,or a looped pipe that is full of water?. If so,in order for the water !current! to flow,there must be a differential in pressure !voltage!. I see no way current can flow in a super conductor,a PM or any other circuit without a potential difference in voltage. It is assumed that a super conductor can produce a magnetic field,but that is not the case. It becomes diamagnetic,as a super conductor will repell both fields of a magnet. So the magnetic field seen in a super conductor is a mirror of the magnetic field that it is exposed to. Magnetic fields are actually excluded from super conductors-this is called the Meissner effect. You may be confused to what they call the induced super currents,which are the mirror field of the PM above the super conductive surface.

MarkE

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Re: Measuring Amps on output coils
« Reply #17 on: March 22, 2015, 04:07:20 PM »
Where is it flowing?. In order to have a flow,it must have direction. So in a super conductor,which direction is this flow of current?. The same question would apply to the PM. We often use waterand pipes to explain current flow through a wire. Is a super conductor represented by a bucket full of water,or a looped pipe that is full of water?. If so,in order for the water !current! to flow,there must be a differential in pressure !voltage!. I see no way current can flow in a super conductor,a PM or any other circuit without a potential difference in voltage. It is assumed that a super conductor can produce a magnetic field,but that is not the case. It becomes diamagnetic,as a super conductor will repell both fields of a magnet. So the magnetic field seen in a super conductor is a mirror of the magnetic field that it is exposed to. Magnetic fields are actually excluded from super conductors-this is called the Meissner effect. You may be confused to what they call the induced super currents,which are the mirror field of the PM above the super conductive surface.
It takes energy to initially induce the current.  The current is induced in a super conductor just as it is in an ordinary coil winding.  An induced voltage builds up current in the coil against the inductance of the loop.  Thus work is performed to transfer energy into the magnetic field surrounding the super conductor.

Low-Q

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Re: Measuring Amps on output coils
« Reply #18 on: March 22, 2015, 05:11:20 PM »
Where is it flowing?. In order to have a flow,it must have direction. So in a super conductor,which direction is this flow of current?. The same question would apply to the PM. We often use waterand pipes to explain current flow through a wire. Is a super conductor represented by a bucket full of water,or a looped pipe that is full of water?. If so,in order for the water !current! to flow,there must be a differential in pressure !voltage!. I see no way current can flow in a super conductor,a PM or any other circuit without a potential difference in voltage. It is assumed that a super conductor can produce a magnetic field,but that is not the case. It becomes diamagnetic,as a super conductor will repell both fields of a magnet. So the magnetic field seen in a super conductor is a mirror of the magnetic field that it is exposed to. Magnetic fields are actually excluded from super conductors-this is called the Meissner effect. You may be confused to what they call the induced super currents,which are the mirror field of the PM above the super conductive surface.
If we take water - good you brought it up. It is easier to understand.


The bucket: Waterpressure at the bottom will cause the flow from the hose connected to the buckets bottom. Voltage is pressure. Ampere is the flow. Higher pressure, higher flowrate.


Superconductor: A hose is looped like a donut. Water does not "see" friction in the wall inside, and will continue to flow forever in a loop when it has started.


Have you ever tried the experiment at school when you cool down an object that becoms super conductive when cooled down?
Placing a magnet on top of it will cause the magnet to hover.
When you approach the magnet, eddy currents are starting to build up in the superconductor and keep flowing - making an equal and oposite magnetic field. This current is continuing to flow "forever" as long the object is superconductive, but no voltage is applied - only the "pressure" from the magnet you put over it. No matter how the magnet will move (up, down or sideways) the superconductor is "charged" by eddy currents that all the time reposition the magnetic field respectively to the magnets position. That is why the magnet is hovering at the same place and not fall off to the sides. If you press the magnet further down, more eddy curent builds up, also the magnetic field from the superconductor increase, and is stronger than the magnets weight. The magnt returns back to the same position again - balancing between its weight and the magnetic force from the superconductor trying to push it away.


Vidar

tinman

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Re: Measuring Amps on output coils
« Reply #19 on: March 22, 2015, 08:33:38 PM »
It takes energy to initially induce the current.  The current is induced in a super conductor just as it is in an ordinary coil winding.  An induced voltage builds up current in the coil against the inductance of the loop.
Quote
Thus work is performed to transfer energy into the magnetic field surrounding the super conductor.
There is no magnetic field surrounding a super conductor.

MileHigh

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Re: Measuring Amps on output coils
« Reply #20 on: March 22, 2015, 08:39:20 PM »
There is no magnetic field surrounding a super conductor.

If I recall correctly there is no magnetic field inside a superconductor.  But of course there is a magnetic field outside a superconductor.

Put a "black box" around the superconducting wire.  So what do you have?  All that you know is that current is flowing through the black box.  Therefore outside the black box there is a magnetic field.

MarkE

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Re: Measuring Amps on output coils
« Reply #21 on: March 22, 2015, 10:44:11 PM »
There is no magnetic field surrounding a super conductor.
That's just wrong.  The Meissner Effect causes a super conductor to reject all external magnetic fields from penetrating inside the superconductor.  The fields inside and outside are very real and very useful, or at least entertaining.  Here is a very fun instructive demonstration by the Royal Society.  https://www.youtube.com/watch?v=zPqEEZa2Gis  Here is another fun demo:  https://www.youtube.com/watch?v=VyOtIsnG71U.

TinselKoala

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Re: Measuring Amps on output coils
« Reply #22 on: March 22, 2015, 11:24:32 PM »
And here's my demo of an interesting effect using a superconductor and a magnet:

http://www.youtube.com/watch?v=JRby1Wilv-Q

MarkE

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Re: Measuring Amps on output coils
« Reply #23 on: March 22, 2015, 11:36:31 PM »
And here's my demo of an interesting effect using a superconductor and a magnet:

http://www.youtube.com/watch?v=JRby1Wilv-Q
I always enjoyed that demonstration.

TinselKoala

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Re: Measuring Amps on output coils
« Reply #24 on: March 22, 2015, 11:59:49 PM »
I always enjoyed that demonstration.
Yes, it's a good one and leads-out much thought and speculation.

One question that immediately arises is this: Does the magnet always wind up rotating in the same direction or sense?
No... it does not. It can rotate in either direction once it gets started.

I have also done the experiment using a larger disc magnet, about the size and shape of a US quarter-dollar coin, completely
wrapped in copper foil. My thinking was that this should help to equalize any thermal gradient across the magnet. It still rotates.

The superconductor is a YBCO type, melt-textured and sintered, prepared according to formulae and directions from Eugene Podkletnov.

MarkE

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Re: Measuring Amps on output coils
« Reply #25 on: March 23, 2015, 12:56:30 AM »
Yes, it's a good one and leads-out much thought and speculation.

One question that immediately arises is this: Does the magnet always wind up rotating in the same direction or sense?
No... it does not. It can rotate in either direction once it gets started.

I have also done the experiment using a larger disc magnet, about the size and shape of a US quarter-dollar coin, completely
wrapped in copper foil. My thinking was that this should help to equalize any thermal gradient across the magnet. It still rotates.

The superconductor is a YBCO type, melt-textured and sintered, prepared according to formulae and directions from Eugene Podkletnov.
It is a brain teaser.  I am inclined to think that it is thermal gradients changing the magnet force top to bottom that drive the thing.  Foil is so-so as a thermal conductor because of the aspect ratio.  If you were to come up with copper or aluminum cup halves with reasonably thick walls to place the disc magnet in, then I think you would see the oscillations damp.  Unfortunately, part of that would be due to eddy current braking. 

An alternative experiment might be to cover the vessel placing the pressure vent holes off to the sides so that gas currents and temperature gradients are mostly lateral.  Thinking off the cuff a pair of concentric plastic domes with a barrier above the vent holes should really reduce both gradients in the region of the magnet.

tinman

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Re: Measuring Amps on output coils
« Reply #26 on: March 23, 2015, 03:22:55 AM »
That's just wrong.  The Meissner Effect causes a super conductor to reject all external magnetic fields from penetrating inside the superconductor.  The fields inside and outside are very real and very useful, or at least entertaining.  Here is a very fun instructive demonstration by the Royal Society.  https://www.youtube.com/watch?v=zPqEEZa2Gis  Here is another fun demo:  https://www.youtube.com/watch?v=VyOtIsnG71U.
The magnetic field is introduced/induced by the PM, a super conductor dose not have a magnetic field unless one is introduced/induced by a PM or electromagnet. Cool the super conductor down without introducing a magnetic field, and try to get a magnetic material to stick to it. You see the super conductor is held so far off the track wether upsidedown or on top of the track. The same effect can be done with standard PMs

MarkE

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Re: Measuring Amps on output coils
« Reply #27 on: March 23, 2015, 03:33:29 AM »
The magnetic field is introduced/induced by the PM, a super conductor dose not have a magnetic field unless one is introduced/induced by a PM or electromagnet. Cool the super conductor down without introducing a magnetic field, and try to get a magnetic material to stick to it. You see the super conductor is held so far off the track wether upsidedown or on top of the track. The same effect can be done with standard PMs
The magnetic field that we are concerned with is the one poled into the superconductor.  Each of those demonstratins does that.  Try and get a copper bar to float underneath strong magnets.  It will slowly fall a short distance and then drop very fast.

tinman

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Re: Measuring Amps on output coils
« Reply #28 on: March 23, 2015, 05:18:30 AM »
The magnetic field that we are concerned with is the one poled into the superconductor.  Each of those demonstratins does that.  Try and get a copper bar to float underneath strong magnets.  It will slowly fall a short distance and then drop very fast.
And once this field is poled into the super cooled material , you believe a current is now flowing through that material?-without a voltage potential?
As I said, the same effect can be done with magnets arranged in a particular fashion.

MarkE

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Re: Measuring Amps on output coils
« Reply #29 on: March 23, 2015, 05:45:25 AM »
And once this field is poled into the super cooled material , you believe a current is now flowing through that material?-without a voltage potential?
As I said, the same effect can be done with magnets arranged in a particular fashion.
Superconductors have the unique ability to circulate current without loss:  No sustaining voltage is required to maintain the current.