Magnetic Levitation (electromagnets?) for an 11th grader

[Joe ONeil]

I don't know if this is the right place to put this, but I am very lost as of right now. I am doing my 11th grade physics project on magnetic levitation. From what I can understand, there are 2 "main" types of magnetic levitation, them being with superconductors and with electromagnets. For the sake of simplicity, I think electromagnets would be easier, but I would like to know about both. Almost every single formula I have come across is way above my level of understanding, except for two, but I do not understand how they work or how they tie in with magnetic levitation. One has a name, and it is called the "Lorentz Force Law." The other I cannot find the name of, and I found it on the magnetic levitation wikipedia page. It is "Pmag = (B^2)/(2μ0).

Some main questions or topics I need help with:
1) The formulas - what do they mean and how do they tie into magnetic levitation
2) Superconductors and levitation - why do they need to be so cold

Thanks in advance!

 

[anorlunda]

Congratulation on your project. It may prove to be challenging. There are others here at PF who can advise you better than I, but here are just a few thoughts.

1. Wikipedia is a great resource for basic information. Not advanced but basic. For example, this article may well answer some of your questions. https://en.wikipedia.org/wiki/Lorentz_force
2. You can experiment with magnetic forces using simple bar magnets. You'll see that like poles repel each other while opposite poles attrace. The only difference between a force and levitation is how strong the force is. https://en.wikipedia.org/wiki/Magnetic_levitation
3. A superconducting magnet is still an electromagnet. Superconductivity means zero electric resistance. So we can put more current through smaller wires if they are superconductive. More current and smaller wires means stronger and smaller electromagnets. Make it strong enough and you can levitate things. https://en.wikipedia.org/wiki/Superconducting_magnet
4. Resistance and superconductivity are properties of materials that are very dependent on temperature. In most cases, materials become superconducting only when they are very cold. https://en.wikipedia.org/wiki/Superconductivity

At the bottom of every Wikipedia article is a list of references pointing you to more authoritative sources.

We are happy to help students here at PF, but remember that asking questions is not the best way to learn most subjects. Study, articles, books, and lectures are better methods for learning.

 

[lekh2003]

2) Superconductors and levitation - why do they need to be so cold

Superconductors have zero resistance and a maximum current running through them which makes the ideal for electromagnets, recall the equation for the strength of a solenoid and you will see how much easier superconducting wire is to create massive magnetic strength.

So the quest to find superconductors never started with looking for superconductors. There was a rule known as the Matthiessen's rule. This rule took into account several effects affecting resistance in wires and conductors and graphed it against temperature. This is a graph of the theoretical Matthiessen's rule (for gold):

Scientists didn't really expect the metal to literally touch zero, so a physicist by the name of Heike Onnes decided to try it out. He found that the conductors literally had zero resistance. Not "for all practical purposes", it was literally zero.

My explanation is quite makeshift, look more at this link: http://www.explainthatstuff.com/superconductors.html

 

[f95toli]

1. A superconducting magnet is still an electromagnet. Superconductivity means zero electric resistance. So we can put more current through smaller wires if they are superconductive. More current and smaller wires means stronger and smaller electromagnets.

This is correct. However, I suspect the OP is referring to levitation using the Meissner effect; where a strong permanent magnet is made to levitate above a (type II) superconductor. The latter is typically a high-Tc superconductor cooled using liquid nitrogen.