Magnet Myths and Misconceptions

[tinman]

In a magnet, the magnetic field is produced by many little magnets.  That is why when you pass a wire through a continuous magnetic field (surface of a magnet), it produces current flow.  The same principle in a standard generator is also working in a homopolar generator.  The homopolar generator that has a brush on the outside of the rotor and a contact on the center of the rotor, takes the shortest path, which is a straight path (virtual wire) which is the lowest resistance path.  This "virtual wire" is only present when the rotor is spun, as that is the only time when a current is produced.  The magnetic field combines with relative motion to produce current flow.  That current flow will act like a wire that passes through a magnetic field.  The reason the voltage is low is because the wire is short.  The reason the current is high, is because the conductive platter performs as a wide, flat wire.  The movement of the wire, is due to the rotation of the platter, and the moving contact on the rotor, constantly moving the position of the wire in the magnetic field.  Faster rotation produces more output current.  A stronger magnetic field will also produce a stronger current.

With the above in mind, rethink how you understand the operation of the twin disk homopolar generator.

Liberty

Liberty
The reason you get a current flow when passing a wire through a continuous magnetic fiels is because the strength of that field cutting through the wire is growing as your wire approaches that field, and  diminishing as your wire leaves the field-AC current.The magnetic field in relation to the disk is constant and dose not change in strength-regardless of your virtual wire or not. Your virtual wire is alway in a constant(unchanging) magnetic field,regardless of where that virtual wire may be on the disk.

The twin disk HP generator has a full loop around the outer perimeter of both disk-this is the current flow conection between both disk,so there is no one contact point or virtual wire as you say. The output is then taken from the center of each disk shaft.There is also Tesla's design of a twin disk HP generator,which uses a steel belt to transfer current from one disk to the other. This also has a contact of 180* around each disk.
So you see,this virtual wire you speak of is not how the HP generator  is working,and thus the law of magnetic induction dosnt apply.

[Liberty]

Liberty
The reason you get a current flow when passing a wire through a continuous magnetic fiels is because the strength of that field cutting through the wire is growing as your wire approaches that field, and  diminishing as your wire leaves the field-AC current.The magnetic field in relation to the disk is constant and dose not change in strength-regardless of your virtual wire or not. Your virtual wire is alway in a constant(unchanging) magnetic field,regardless of where that virtual wire may be on the disk.

The twin disk HP generator has a full loop around the outer perimeter of both disk-this is the current flow conection between both disk,so there is no one contact point or virtual wire as you say. The output is then taken from the center of each disk shaft.There is also Tesla's design of a twin disk HP generator,which uses a steel belt to transfer current from one disk to the other. This also has a contact of 180* around each disk.
So you see,this virtual wire you speak of is not how the HP generator  is working,and thus the law of magnetic induction dosnt apply.

I would agree that a current is generated as a coil approaches a magnet and as it leaves a magnet.  (Standard generator).  Further, it is known that a wire (not a coil) passing over a continuous (unchanging) magnetic field produces a current in the wire, as long as motion is present between the wire and magnetic field.  However, in this case, you cannot use a loop of wire (coil), as the current will cancel, and there will be no output.    In the case of the magnetic field being constant in relation to the disk, the latter case is the known reason for current flow.  It is the wire (conductive path) passing through a constant magnetic field (acting as a wire) that will produce a current.  Mr. Faraday was actually correct about induction, and is the basis of operation of the Faraday (HP) generator and the standard generator.

Liberty

[Newton II]

Some things that stand out in a homopolar generator that may hold the answers are-
1-Stronger the magnetic field through the disk-the more current is produced.
2-The faster the rotation of the disk-the more current is produced.
Some odd things are-
1-reverse rotation of disk(with magnetic field in same polarity),and the current flow is reversed.
2-reverse the polarity of the magnetic field through the disk,and the current flow is reversed.
3-Current is produced weather the magnets are fixed or rotate with the copper disk.
4-Current isnt produced if the disk is fixed,and magnets are rotated around the disk.

It may be for the reason that when you rotate the disc, the outer edge of the disc moves with higher velocity than inner edges of the disc to catch up with RPM. This may create some sort of 'gradient' or 'potential difference'  between  rim  and the centre making the electrons to flow.

In that case if you use a disc of very large diameter, it should produce a considerable gradient creating a higher voltage,  current flow depending on strength of magnetic field.

So, instead of using one thick disc if you use several thin discs separated and placed one above the other and rotate in a uniform perpendicular magnetic field, will it not improve the efficiency of the generator?

The explanations look  cranky,  but if you go on throwing arrows in the dark,  some arrow would reach the destination!

[tinman]

I would agree that a current is generated as a coil approaches a magnet and as it leaves a magnet.  (Standard generator).  Further, it is known that a wire (not a coil) passing over a continuous (unchanging) magnetic field produces a current in the wire, as long as motion is present between the wire and magnetic field.  However, in this case, you cannot use a loop of wire (coil), as the current will cancel, and there will be no output.    In the case of the magnetic field being constant in relation to the disk, the latter case is the known reason for current flow.  It is the wire (conductive path) passing through a constant magnetic field (acting as a wire) that will produce a current.  Mr. Faraday was actually correct about induction, and is the basis of operation of the Faraday (HP) generator and the standard generator.

Liberty

LibertyThe wire(conductive path) dosnt pass through a constant magnetic field,it remains in a constant position in relation to the magnetic field,as the brush on the outer rim never changes position-thus the line(potential wire)between the outer brush and center brush is stationary(fixed) just as the magnetic field is.There is no increase or decrease of magnetic field strength,nor is there a moving wire passing over that constant magnetic field(as the two brushes are in a fixed position)-so there is no induction taking place.In order to fully understand as to how the HPG work's,we need to know what exactly a magnetic field is. And in order to know what a magnetic field is,we need to know how the HPG work's-the two go together in understanding each other.

[Liberty]

It may be for the reason that when you rotate the disc, the outer edge of the disc moves with higher velocity than inner edges of the disc to catch up with RPM. This may create some sort of 'gradient' or 'potential difference'  between  rim  and the centre making the electrons to flow.

In that case if you use a disc of very large diameter, it should produce a considerable gradient creating a higher voltage,  current flow depending on strength of magnetic field.

So, instead of using one thick disc if you use several thin discs separated and placed one above the other and rotate in a uniform perpendicular magnetic field, will it not improve the efficiency of the generator?

The explanations look  cranky,  but if you go on throwing arrows in the dark,  some arrow would reach the destination!

I agree with Newton II's explanation and think that there is merit in the "potential difference" theory (due to the difference in velocity from inside the disk, to outside, while immersed in a magnetic field, (to separate charge, preventing the charge from shorting out in the disk like an eddy current)). And in order for current to flow, it would have to form a conductive path to allow output of this generator to a load.  This may account for the other HP generators that Tinman was referring to.  For HP generators in general, it appears that the larger, the more it produces.  But as in magnet motors that operate on the gradient method, (magnet spiral style motor) the difference (gradient) is fairly small. 

Liberty