29 Jun, 2013
PRESENTATION: The diamagnetic substances like graphite are repelled by the magnetic field sources. If we place a sheet of pyrolytic graphite over four powerful magnets facing each other, we can see that it is kept levitating because its weight is balanced by the repulsion magnetic force.
- More Diamagnetism Demonstrations, Chris Conery, L. F. Goodrich, and T. C. Stauffer, Phys. Teach. 41, 74 (2003).
- A Simple Diamagnetic Levitation Experiment, Ron Edge, Phys. Teach. 41, 122 (2003)
INTRODUCTION: In electromagnetism, diamagnetism is a property of the materials which consists in being repelled by magnets. It is the opposite case of the ferromagnetic materials, which are attracted by magnets. The phenomenon of diamagnetism was discovered and labeled for the first time in September 1845 by Michael Faraday. Examples of diamagnetic materials are graphite, bismuth, copper, bronze,….
OBJECTIVE: to produce the levitation of a diamagnetic material over 4 magnets that are facing each other.
MATERIALS: four magnetic cubes, a small square pyrolytic graphite plate.
SETUP: the four magnets are placed forming a square in such a way that the two magnets in the same diagonal keep the same orientation between them and the opposite to the perpendicular diagonal. The alternating disposition is necessary to achieve the levitating effect. If they are placed in a different way they will not levitate. Then the graphite plate is placed over the magnets and we can observe how the plate floats over the four magnets. As a curiosity, we can add that there is no time limit, but the plate will float all the time one wishes.
EXPLANATION: In this experiment, thanks to the diamagnetic properties of graphite, we make a small plate of this material levitate over a set of magnets. This levitation is due to the peculiar disposition of the magnets, which gives shape to repulsion forces over a graphite plate. These make levitation notably stable, allowing for oscillation over its equilibrium position,
CONCEPTS: diamagnetism, magnetic levitation, magnetic field, magnet, diamagnetic materials.
- Tipler P.A. Física, Reverté, 2010.
- De Juana J.M., Física General, Pearson, 2009.
- Serway R.A, Jewett J.W., Física, Thomson-Paraninfo, 2010.
- Teplitz D., Electromagnetism. Paths to research, Plenum Press, 1982.
- Cheng D.K., Fundamentos de electromagnetismo para ingeniería, Alhambra Mexicana, 1998.
STUDENTS 2012-2013: Lucas Álvarez, Alejandro Andrade, Adrián Martínez, Carolina Rodríguez.
LINK pdf STUDENTS (in Spanish):