1. May 17, 2005

bijanv

Hey everyone, for my end of the year project for my grade 11 physics class I am hoping to be able to do the "frog levitation" lab that has been done before but is quite interesting.

My question is that can you create a solenoid (using simple materials found at local stores) strong enough to counter balance the gravitational force on the frog? And if not a frog how about a strawberry or something like that.

Also I saw a video of floating water, how is this experiment done? :grumpy:

Any help would be appreaciated! Thanks in advance!! :rofl:

2. May 17, 2005

Gokul43201

Staff Emeritus
You will need a 10T coil to levitate a frog. There's no way this can be done using "materials found at local stores". Typically, you use a superconducting magnet to get anywhere over a Tesla. Even strawberries are too heavy...but you might be able to levitate a tiny drop of water with a conventional solenoidal magnet, but I don't imagine it will be particularly easy.

As for how the experiment is done...I imagine you turn on the magnet to full strength very slowly (magnet held vertically, with field lines pointing up) and carefully place a tiny drop of water right above the (along the axis of the) solenoid....and pray it floats. Since I have little experience, playing with conventional magnets, I won't say much more just yet.

And if you're asking how this works, the short answer to that is : diamagnetism. Water is a diamagnetic material, so anything with lots of water in it will partially expell a magnetic field. This makes the thing feel a repulsive force from the magnet. If the force is strong enough to balance the weight, the thing will float.

3. May 18, 2005

bijanv

thx for the info.. is a 10T coil the minimum strength I would need or would it work fine with that?

Edit: Where could I find 10T coils? I have been searching on google and no results yet :grumpy:

4. May 18, 2005

FredGarvin

I think you should try to get a relative feeling for just how large 10T is Bijanv.

Here's a hint:

5. May 18, 2005

bijanv

ok.... well then.. i guess that answers my question

thanks alot guys

6. May 18, 2005

zoobyshoe

Wouls you settle for a copper or aluminum ring, "levitated" with AC? You could probably do this setup yourself.

7. May 18, 2005

Gokul43201

Staff Emeritus
[sidetrack]Fred, where did you get that quote from ? I find it very hard to believe that 14.7T was the record in 2001. We have a 16.2T magnet in our lab, and it's over 5 yrs old. [/sidetrack]

I think zoob has a nice idea. I thin aluminum washer shouldn't be terribly hard to levitate. Al (or Cu) has a diamagnetic susceptibility that is much bigger than that of water.

8. May 18, 2005

zoobyshoe

Actually, the setup I'm suggesting doesn't work by diamagnetism.

Basically you wind your solenoid aound a ferrous rod, mount it so the rod is sticking up vertically, and slip a conducting ring onto the rod. When the coil is energized by AC it induces current to flow around the conducting ring which also creates a magnetic field. The ring's field is always opposed to the solenoid's field (like poles facing) so they always repell each other.

You need the right current in the coil to prevent the ring from just shooting off the rod. It also gets hot quickly, so you have to keep your demonstration times to a minimum.

9. May 19, 2005

Gokul43201

Staff Emeritus
Having thus revealed my ignorance of tesla coil fun and games, I shall keep a tight lid on it.

So Zoob, all you would need is a variac, a solenoid, an iron core and the ring ?

10. May 19, 2005

zoobyshoe

That's the whole show, except for a secure mount for the rod/solenoid.

I have seen plans for these in many Fun Projects With Electricity type books, but haven't ever made one myself. If bijanv did some googling he might find some plans all specified out for him. Otherwise someone might have some suggestions about the guage of the wire he should try in his solenoid, as well as a suggested # of turns, based on what he wants to accomplish, and safety considerations. Or, he may have had his heart set on a frog, and no longer be reading this.

11. May 19, 2005

Gokul43201

Staff Emeritus
Ummm yeah. When you start off with hopes of making a leap-frog, it's a little disappointing to have to settle for a ring-toss.

12. May 19, 2005

FredGarvin

Crud. I thought I put up the link. I'll find it! Hold on a sec!

Here it is. I stumbled across it, so I can not verify the source of the record claim, but the relative magnitude of the magnetic field strength is what I was going for.

http://enews.lbl.gov/Science-Articles/Archive/14-tesla-magnet.html

Last edited: May 19, 2005