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MIT Physics 8.02 - Electricity & Magnetism

SECTION : Faraday's Law       

Moving Monopole 3D
Moving Monopole 2D
SUBJECT: Monopole Moving Above A Conducting Plane  

In the top figure, we show the field lines of a magnetic monopole moving to the right above a thin conducting plane. As the movie progresses, the monopole goes from zero speed to very high speed. Intially the region below the plane is not shielded from the magnetic field, but as time progresses and the monopole moves faster and faster,, the magnetic flux below the plane is increasingly excluded from that region, with the field in advance of the monopole excluded first. At very high speeds the flux is totally excluded from the region z < 0. There is a short pause at the beginning of the movie when we hold everything fixed, and then the monopole begins to move. The camera follows the monopole so that it appears to be at rest even though it is moving faster and faster. On the plane below the monopole we show the eddy currents in the plane which are induced by the motion of the monopole.

In the second figure, we show the field lines in the plane containing the monopole and the normal to the plane, along with the color coded field strength. The images are color coded according to the magnitude of the magnetic field, ranging from very strong (white) to very low (black), with an over all blue hue.

You will need a QuickTime movie player to play these mp4 movies.

If you are interested in the details of how this is calculated, we are following the classic paper of W. M. Saslow, “Maxwell’s Theory of Eddy Currents in Thin Conducting Sheet, and Applications to Electromagnetic Shielding and MAGLEV,” Am. J. Phys. 60 (8), 693-711 (1992).