Help with electromagnets acting at a distance on an object

[Neekman99]

Would the model in this diagram be able to keep the object stationary provided there is enough current? What equations would be used to calculate the forces acting on the object from the electromagnetic fields?
-The object is equidistant from the electromagnets
- The object is separated from the electromagnets by air
- The object is 0.5k
- There is an upward force on the object of 200N
The idea is that the lower electromagnet provides a force upwards on the object and the upper EM acts downwards on the object.
Any help would be much appreciated.
https://www.physicsforums.com/attachments/234009

 

[davenn]

Would the model in this diagram be able to keep the object stationary provided there is enough current?

first thoughts would be, is that your electro-magnets are orientated incorrectly ... should be end on, not side on

 

[Neekman99]

first thoughts would be, is that your electro-magnets are orientated incorrectly ... should be end on, not side on

Very true

 

[berkeman]

Would the model in this diagram be able to keep the object stationary provided there is enough current? What equations would be used to calculate the forces acting on the object from the electromagnetic fields?

Welcome to the PF.

Have you read this introductory article about Magnetic Levitation? https://en.wikipedia.org/wiki/Magnetic_levitation

 

[dlbeeson]

Would the model in this diagram be able to keep the object stationary provided there is enough current? What equations would be used to calculate the forces acting on the object from the electromagnetic fields?
-The object is equidistant from the electromagnets
- The object is separated from the electromagnets by air
- The object is 0.5k
- There is an upward force on the object of 200N
The idea is that the lower electromagnet provides a force upwards on the object and the upper EM acts downwards on the object.
Any help would be much appreciated.
https://www.physicsforums.com/attachments/234009

Neekman99, IF you are trying to levitate a non-magnetized piece of iron or ferromagnetic material, like a little toy steel airplane, I believe you will find that the extremely fine balance between upward and downward forces will be almost impossible to achieve. The object will be pulled one way or another. What is being done instead is only one magnet, on the top, pulling the object up. Of course, if constantly on, it would pull the object to the magnet, so a position sensor is used, to tell when the item is in the proper position. The sensor turns off the magnet. The item starts to fall, the position sensor turns on the magnet, pulling the object up. when in position, the position sensor turns the magnet off. While it may seem the object would oscillate up and down, the fast response of the position sensor actually holds the object very close to stationary. Conversely, if you want to levitate from the bottom, like hidden under a wood desk or gray glass table, the object can not be ferromagnetic, but electrically conductive, like an aluminum disk, say a toy flying saucer shape. Then the electromagnet underneath is run with AC. The AC induces a current in the conductive object, which produces an opposing magnetic field. So the bottom electromagnet repels the non-magnetic/conductive object. Coil design must repel more on the outside, and less on the inside, to keep the repelled object centered, else it would "slide" off to the side. See Eric Roberts Laithwaite, the father of levitation.

 

[Vanadium 50]

first thoughts would be, is that your electro-magnets are orientated incorrectly ... should be end on, not side on

Second thought is that it's not enough for the forces to balance. There has to be a restoring force opposite to the direction of displacement in all directions. I don't believe that your setup does this, and I also believe that Earnshaw's Theorem prevents it.

 

[CWatters]

Most likely it will pop out sideways.

 

[Neekman99]

Welcome to the PF.

Have you read this introductory article about Magnetic Levitation? https://en.wikipedia.org/wiki/Magnetic_levitation

I have now :) Very helpful, thanks.

 

[Neekman99]

Neekman99, IF you are trying to levitate a non-magnetized piece of iron or ferromagnetic material, like a little toy steel airplane, I believe you will find that the extremely fine balance between upward and downward forces will be almost impossible to achieve. The object will be pulled one way or another. What is being done instead is only one magnet, on the top, pulling the object up. Of course, if constantly on, it would pull the object to the magnet, so a position sensor is used, to tell when the item is in the proper position. The sensor turns off the magnet. The item starts to fall, the position sensor turns on the magnet, pulling the object up. when in position, the position sensor turns the magnet off. While it may seem the object would oscillate up and down, the fast response of the position sensor actually holds the object very close to stationary. Conversely, if you want to levitate from the bottom, like hidden under a wood desk or gray glass table, the object can not be ferromagnetic, but electrically conductive, like an aluminum disk, say a toy flying saucer shape. Then the electromagnet underneath is run with AC. The AC induces a current in the conductive object, which produces an opposing magnetic field. So the bottom electromagnet repels the non-magnetic/conductive object. Coil design must repel more on the outside, and less on the inside, to keep the repelled object centered, else it would "slide" off to the side. See Eric Roberts Laithwaite, the father of levitation.

Ok understood. That's helped me out a lot with this, much appreciated mate!