# Induction vs electromagnetic repulsion: which is more efficient?

1. Oct 30, 2009

### MaJiK9021

Hi, I am curious about the most efficient method of levitating an object. I am considering using electromagnetic induction or the repulsion between a magnet and electromagnet. Which would require less energy? Also I am aware of Earnshaw's law; let's ignore the complexities it causes for now.

Also, is it possible to produce a repulsive force through induction, if the electromagnet is not moving in relation to the conductor? Say, if the electromagnet and the conductor are fixed in spot, but the electromagnet has an alternating magnetic field.

Any help would be appreciated.

2. Oct 31, 2009

### Bob S

Yes, eddy-current repulsion is possible whenever there is a conducting loop or plate in a dB/dt field (Faraday's law). The induced currents are replused by the magnetic field (Lorentz force). It is sometimes used in circuit breakers, for example.
Bob S
 See section on eddy current repulsion in
http://en.wikipedia.org/wiki/Eddy_current
 There cannot be an axial force on a conducting ring with azimuthal induced currents unless the magnetic field has an r component (i.e., has a dB/dz gradient).

Last edited: Oct 31, 2009