labview1958

Does the repulsive follows the inverse square law? Or does it follow the inverse cube law? or does it the inverse cube law?

If z is the separation distance & x is a constant, does it follow F=AEXP(-zx) or does it follow F=AZ^x?

Let's say I have a magnet on the edge of a table. I bring a rotating copper disc near to the edge of the magnet on the table. What will happen?

a. the magnet stays put.

b. the magnet lifts of

c. the magnet is pushed away from the edge but is still on the table.

Here's the diagram

rotating copper disc .........magnet on edge of table

magnet height is 5 cm and the base 1cm X 1cm

I have been playing around with different types of magnets. I have used two identical cylindirical magnets to fiind the repulsive force between them for various separation distances. I have also used rectangular magnets for similar purposes. Also I have used other shapes like square etc. What I found was that

F = Aexp(-zx) which is an exponential curve

While most textbooks say it should be F=AX^z which is a power series.

where F = repulsive force and x = distance between magnets.

The expression F = Aexp(-zx) is valid for the repulsive force between a bulk superconductor and a magnet. It should also be valid for repulsion between identical magnets.

If the magnets are half the size of the superconductor, would the presence of the superconductor increase/decrease the magnetic force repulsion/attraction between the two magnets as compared when there is no superconductor? My hunch is that there would be a shielding effect that reduces the magnetic force. From your diagram it is clear that the field lines have changed, thus the value of the attractive force would be reduced.

Any comments about the arrangement below?

S

magnet

N

N

superconductor disk

S

S

magnet

N

Does the presence of the superconductor reduces the attraction between the magnets? Is the superconductor acting like a shield?

Does anyone know how much liquid nitrogen is required to change the temperature of a copper sphere weighing 100 grams from room temperature to 77K? Once there how much more liquid nitrogen is required to keep the copper sphere at 77K for 1 hour? Anyway how to measure the temperature of the copper sphere?

I bought the superconductor type 2 disc from an internet site. I cannot recall the name. However they are not expensive. For liquid nitrogen you can buy from the factory for USD 1.00 per litre. You can cool it and make it levitate but when I try to move the magnet the superconductor runs out and falls. Sometimes for some unkown reason the bottom superconductor will jump up and stick with the superconductor. Can anyone explain?

I want to levitate a type 2 superconducting disk between two permanent

magnets. One magnet is below the superconductor and one is above the

superconductor. Here is a sketch.

S

magnet

N

N

superconductor disk

S

S

magnet

N

Is it possible? If the lower magnet is glued to a table and the upper magnet

moved further up, would the superconductor move up or down?

If the mu-material is iron, it would shield the magnetic field. Thus the field would be weaker above the mu-material. I assume the field would also be weaker on the side of the mu-material.

I want to levitate a type 2 superconducting disk between two permanent

magnets. One magnet is below the superconductor and one is above the

superconductor. Here is a sketch.

S

magnet

N

N

superconductor disk

S

S

magnet

N

Is it possible? If the lower magnet is glued to a table and the upper magnet

moved further up, would the superconductor move up or down?

Is there a way of placing 10 magnets of 0.1 Tesla each to get a total of 1 Tesla? If not 1 Tesla do we get 0.2 Tesla?

Is my maths correct?

Let's say each bar magnet has 1 Tesla. Then 10 bar magnets put together would have 10x0.1 = 1 Tesla

Is it right? Can I get 1 Tesla?

I have been trying to increase the strength of a magnetic field by putting together 10 bar magnets. Let's say each bar magnet has 1 Tesla. Then 10 bar magnets put together would have 10x0.1 = 1 Tesla. So far I have not been successful. Is it possible?

Is this correct?

B = mu*N*I = mu*total current

This means there is no difference between a solenoid model and a current filament model!

If the magnet is small compared to the disk then the height of levitation would always be the SAME for the same magnet but different types of superconductors which exhibit the meisnner effect. Is there any good theory or experimental data to back this hunch?

I want to levitate a magnet on a superconductor. Out of curiosity I want to know whether the height of levitation varies with different superconductors. My hunch is that for the SAME magnet but DIFFERENT superconductors the height of levitation is the same. Is that TRUE?

Anyway the formula :

B = mu*N*i

only gives the FIELD in the centre of the magnet. What about the field at "z" distance from the solenoid. Furthermore the magnet does not have "N" turns of the coil.

Whatever the suggested formula, it must be remembered that a permanent coil does not have N ( number of coils). Thus those equations cannot be used. Is there any other way?

Would it be right to say that for a superconductor, the conductivity is infinite? If it so than than w = 0 thus Lift force = (Mu*I*I/4*pi*h). If I put a permanent magnet on a superconductor would the lift force follow the above formula? How do I measure/calculate the current? If I know the levitation height and the weight of the permanent magnet can I calculate the current. Is this reasoning sound?

Thus mgh = Mu*I*I/4*pi*h

I*I = m*g*pi*4/Mu.

Should the levitation height of the same permanent magnet be same for ANY superconductor?

According to Bio-Sarvat Law regarding a long curent carrying wire, the field is given by

B = MU(o)I/2*3.142*r where r is the distance from the wire. It says that the FIELD is inversley proportional to the distance. However we know that the FIELD of a permanent magnet varies as an inverse CUBE. If I model the permanent magnet as a solenoid what would be the SIMPLE formula?

Can a permanent magnet be modelled as a current carrying wire? If have a cylindrical magnet of strength 0.1 Tesla, length 3 cm and radius 1 cm., can I take a wire of length 3 cm, radius of 1cm and pass y Amps of current. Can I model it that way? Or is there a better model!

I am doing a STUDY of EM drag force between a moving conductor and a permanent magnet. I understand that a conductor moving with a velocity v over a permanent magnet will experience a REPULSIVE force. The formula for that force is as follows:

Lift force = (Mu*I*I/4*pi*h)(v*v/(v*v + w*w))

Drag Force = (w/v)*Lift Force

w=2/(mu*sigma*delta)

Mu = magnetic permeabilty of vacum

I = Current generated in conductor

h = separation between permagnet and conductor

v = velocity of conductor

w = charateristic velocity

sigma = conductivity of conductor

delta = conductor thickness.

w = The velocity where the EM DRAG is maximum

w=2/(mu*sigma*delta)

The formula shows that the charateristic velocity varies inversley with the thickness of the conductor. This means:

1. If thickness approaches ZERO w approaches infinity!

2. If thickness approaches infinity w approaches zero!

Are these deductions correct.? What part does the EDDY CURRENT penetration depth plays in this?

Anyone OUT there?

When a MAGLEV (Levitating Train) travels over Copper/Aluminum Sheet it levitates and is propel forwards. This is because there are magnets on the underside of the train. As the train moves the magnetic field CUTS the copper/aluminum sheet and a mirror image is formed in the copper/aluminium sheet. The mirror magnet and the real magnet REPELS each other. Thus the train levitates. There is EM Lift and EM Drag induced on the train. The RATIO is different for different train speeds.

Anyone can HELP!

Does anyone know where can I get a table regarding LIFT/DRAG RATIO for copper of thickness 1mm, 2mm, 3mm etc to 20 mm? Does the EM Lift/Drag Ratio varies with the thickness of copper? If there is no table a formula would suffice!