Hello everyone today we are going to demonstrate principles of vertical levitation using a recreational toy.
This is today's experimental setup. It contains this plastic globe and this vertical magnetic stand.
There is a permanent magnet in the upper part of this globe and an iron core in the magnetic stand.
The iron core and the permanent magnet attract each other.
We know that the electromagnetic forces vary with distance.
If these parts are close to each other, forces are stronger than if they are apart.
So, it should be possible to make this globe levitate in thin air,
if we found a position where the attraction force is equal to the globe's weight.
And, yes, this would be true, if not for a very important detail.
In that point where weight is equal to the attraction force, we have what is called an  unstable balance.
The resultant force acting over the globe increases if it moves out of the balanced position.
So, how do we turn this device into something that makes levitation really possible?
There is a trick to make this work.
This magnetic stand is also equipped with an electromagnet.
So, it is possible to control magnetic flux by varying the current being fed to the coil.
When the globe goes above this balance point, magnetic flux in the upper part is reduced, also reducing the attraction force.
When it goes below this balance point, magnetic flux is increased, also increasing the attraction force.
When we turn on this device we enable automatic control.
So, due to this kind of control, instead of having a single balance point that is practically unachievable in real life
We now have a stable region for operation.
Thank you for your attention. I hope this video was useful for you.
In the next video, we will see a different example of levitation, that uses the same principle.
