Magnetic Levitation

[@dramorak1]

Every video I watch is gold. Practical, simple, and concise.

[@ElectromagneticVideos]

Thanks! That's exactly what I am aiming for although I sometimes fail on the concise part!

[@sciencegeekgrandpa8]

How would varying the frequency affect the levitation?

[@ElectromagneticVideos]

That is a great question! I think (and emphasize think - these are just my immediate thoughts) that the levitating force would drop because of the the skin depth. The skin depth is how much/far an EM field of a given frequency penetrates into a conducting object. The higher the frequency the smaller the skin depth. The skin depth for 60Hz used here is about 1cm. If we raise the frequency to 10kHz (and keep the exciting AC power voltage the same) the skin depth for Aluminum is about 1mm, so in a rough sense only the 1mm layer of aluminum closest to the bottom would carry significant current. If we crudely assume the field is uniform (its not) throughout the aluminum, only 1/10 the current will flow. (Or consider the resistance of the 1mm thin later compared to the 1cm=10mm disk = 10x the resistance => 1/10 times the current). So it would seem the levitation would drop. Now if we were to raise the exciting AC voltage to keep the magnetic flux field the same amplitude, that should more than counteract the thinning of the skin depth (depth is proportional to the square root of 1/f) with increased eddy current voltage proportional to frequency so there is more current and levitating force. And and also more heat production because more current through more resistance = more heat). The huge advantage of this is the reduce size of the exciting coil/core. The disadvantage is the increase in heat production. The cheaper coil and increased heat would be why higher frequencies are used in induction stove elements.

[@retrozmachine1189]

Aluminium knob, electromagents and Electromagnetic Videos. I wonder if we are heading towards an examination of how an old spinning disc electricity meter works. If so it might be useful to describe how the meters work in the USA by only having L1/L2 passing through windings while in single voltage countries the hot wire passes through the meter while the neutral wire only provides a voltage reference. P.S. I know how it all works, just some other people may find it interesting.

[@ElectromagneticVideos]

You know, I have one of those meters somewhere! Never though of doing a video about it till you mentioned it - I'll have to see where I stored it. Funnily enough, I recently bought a digital electric power meter evaluation kit that I was hoping to use to use for some power measurements (it has a usb connection for development purposes). Might be nice to do a comparison.

[@retrozmachine1189]

@@ElectromagneticVideos Interesting. I've been down the electronic mains meter path myself. Initially I just had a basic DIN kWh meter that output 1000 pulses per kWh and nothing else. Right now I have a DIN meter that has RS485 output and produces a plethora of information as well as the standard S0 and optical pulse outputs. The bang per buck ratio is pretty impressive these days.

[@ElectromagneticVideos]

@@retrozmachine1189 So you original one sent out one pulse per wh consumed? Clever! Like your RS485 out I'm hoping the usb on mine will also spit out a pile of info. Haven't had time to play with it yet. Yes about the bang for the buck - amazing to think of the capabilities of millions of transistors costing so little these days!

[@Sparky-ww5re]

That is so cool. Maybe you should do a video with a knob made of steel or similar ferrous metal and see if it gets hotter than the aluminum knob, and maybe a steel knob will lift higher for a given current. This experiment looks similar if not identical principle to how an induction stove-top works. Induction ranges are really nice although many are outside my budget in this time of high inflation and higher interest rates and tend to be found mainly on really high end models although the prices have come down significantly in the last decade or so.

[@ElectromagneticVideos]

The steel or other ferrous materials do behave differently - I should have pointed out that in the case of magnetic materials the magnetic attraction due to magnetization of the steel becomes so much stronger than the repulsive effect that the steel becomes solidly attached to the core until the current is removed. You would never notice any repulsive effect. It should work with copper - if I ever come across a suitable piece of copper I will try it. Your absolutely right about inductive tops being similar. Actually the exact same thing in terms of inducing currents that heat the pot or pan. The main difference is they are operated at a few 10s of kHz rather than 60 Hz. Skin depth would be half a mm at 20kHz so the effective resistance of the disk/pot would appear higher and limit the eddy currents which are responsible for the levitation. I wonder if a mm thick plate of aluminum would float on an induction range or if the currents would be too low to generate sufficient repulsive force? Sadly your are right about the prices for inductive ranges. However, I will watch the local Habitat for Humanity ReStore in case one shows up and price suitable for experimentation! Now you have got me really interested!

[@charlesvilanova]

Very interesting

[@ElectromagneticVideos]

Isnt it! And kinda cool to see things float!

[@alphabeets]

Would it theoretically be possible to levitate a human body in this way? If so, what would it take in terms of power and equipment? I imagine it would be lethal to the human body.

[@ElectromagneticVideos]

Its been done to a frog! Look at this video kzbin.info/www/bejne/gZ2tpImnmJWsra8 . It not the same form of magnetic repulsion though . The frog (and us) are diamagnetic so we have a very weak repulsive effect to a magnetic field. They made a huge field to lift the frog. Would be challenge to make a field like that big enough for a person but it would work and the person would probably be Ok afterwards like the frog was! It would be so neat to be levitated like that!

[@scottthomas3792]

Isn't that sort of how older mechanical speedometers worked? A spinning magnet inside an aluminum cup. The indicator needle was attached to the cup.. In high school, one physics class had a electromagnetic " cannon" that fired aluminum rings maybe five feet..the rings fit over a rod with a huge coil at the end, running off a 240 volt air conditioner outlet.

[@ElectromagneticVideos]

I think your right. It may have been the eddy cirrents dragging the cup more and more with speed. Gee - I like that cannon idea! Future video maybe!

[@dogwalker666]

Yes, It's also how the emergency brakes on rollercoasters work.