Floating Frog
I saw on the internet a video of a frog floating in a magnet. How does that happen? Did the frog become magnetized?
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Several videos on the internet show small biological objects apparently defying gravity by floating in the bores of research magnets. An example is shown below. The fields used are very large (on the order of 15T) and the objects are very small (tadpoles, insects, blades of grass).
This is a highly visual and memorable demonstration of diamagnetism. Most biological materials (including human bodies) contain high concentrations of water and are weakly diamagnetic. When placed in an external magnetic field an internal polarization develops that opposes the applied field and a counterbalancing diamagnetic force is generated. If the object is light and the magnetic field is strong, this diamagnetic force is sufficient to eliminate the effects of gravity, allowing the object to "float".
This is a highly visual and memorable demonstration of diamagnetism. Most biological materials (including human bodies) contain high concentrations of water and are weakly diamagnetic. When placed in an external magnetic field an internal polarization develops that opposes the applied field and a counterbalancing diamagnetic force is generated. If the object is light and the magnetic field is strong, this diamagnetic force is sufficient to eliminate the effects of gravity, allowing the object to "float".
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A second form of magnetic levitation using principles similar to those of the “floating frog” can be seen with the Levitron, a commercially available toy. Here is a video that may intrigue you. |
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References
Simon MD, Geim AK. Diamagnetic levitation: flying frogs and floating magnets. J Appl Phys 2000;87:6200-4. (The physics is a little more complicated than the above discussion suggests, in that there is only a small area within the field where stable "levitation" can occur. This paper will take you through the details.)
Simon MD, Geim AK. Diamagnetic levitation: flying frogs and floating magnets. J Appl Phys 2000;87:6200-4. (The physics is a little more complicated than the above discussion suggests, in that there is only a small area within the field where stable "levitation" can occur. This paper will take you through the details.)