### Coil Levitation with Eddy Currents

I tried out a little quickie experiment in the lab this afternoon. In short: a coil with a changing current, (AC), placed on a non-ferromagnetic conductor, like aluminum, will induce an opposing magnetic field and levitate. You can read all about the effect caused by eddy currents, on Wikipedia, and watch what happened in the lab here:

King said…
Hi there,

I have been doing some research into magnetic levitation using eddy currents when I stumbled upon your video here: http://12seconds.tv/channel/dolphus/108842. It is the only video I could find of someone actually doing levitation - which is weird. So I was just wondering if you could answer a few questions about the setup of your experiment. It would be greatly appreciated if you could just tell me the schematics for you experiment:

Was it AC 60Hz 240V power?
Aluminium table you used underneath?
Insulated copper wire in the
King said…
contd...

in the circle?
How many turns of copper wire? (just a guess of how much wire to use?

If you could answer these I would be grateful.

Lance
Hamilton said…
The power was 60Hz 120V regulated through a variac to about 30V. The coil is insulated magnet wire. I don't know, but I suspect there are about 300 turns. It's just an old coil I pulled out of the junk pile. The metal underneath is about 3/4 inch think aluminum.
Magic Tricks said…
Hello, I'am George. Visit my website, if you want to see Tricks with Levitation. All tricks are video explained, so you can learn very easy. Thank's and have a great day.

### Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems, there seem to be fewer explanations of the procedure for deriving the conversion, so here goes!

What do we actually want?

To convert the Cartesian nabla

to the nabla for another coordinate system, say… cylindrical coordinates.

What we’ll need:

1. The Cartesian Nabla:

2. A set of equations relating the Cartesian coordinates to cylindrical coordinates:

3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system:

How to do it:

Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables.

The chain rule can be used to convert a differential operator in terms of one variable into a series of differential operators in terms of othe…

### The Valentine's Day Magnetic Monopole

There's an assymetry to the form of the two Maxwell's equations shown in picture 1.  While the divergence of the electric field is proportional to the electric charge density at a given point, the divergence of the magnetic field is equal to zero.  This is typically explained in the following way.  While we know that electrons, the fundamental electric charge carriers exist, evidence seems to indicate that magnetic monopoles, the particles that would carry magnetic 'charge', either don't exist, or, the energies required to create them are so high that they are exceedingly rare.  That doesn't stop us from looking for them though!

Keeping with the theme of Fairbank[1] and his academic progeny over the semester break, today's post is about the discovery of a magnetic monopole candidate event by one of the Fairbank's graduate students, Blas Cabrera[2].  Cabrera was utilizing a loop type of magnetic monopole detector.  Its operation is in concept very simpl…