Is the Homopolar Motor a Reactionless Drive?

[MS La Moreaux]

If an electric current is passed through a conducting magnet at a right angle to the magnetic field lines, the magnet should experience a force at right angles to both the flux and the current. This is a linear version of the homopolar motor. Since the magnetic field is not attached to the magnet, it would seem that there is no reaction to this force, thus violating Newton's third law of motion.

Mike

 

[Dale]

EM fields always conserve momentum.
http://farside.ph.utexas.edu/teaching/em/lectures/node91.html

You may also want to read this thread starting around post 40
https://www.physicsforums.com/showthread.php?t=287164&page=3

 

[MS La Moreaux]

Thanks for the references, but they seem only to apply to EM fields. The case I described involves only a steady magnetic field and an electric current. The current obviously requires an electric field, but I am not inclined to believe that it is relevant in this case. I realize that it is unlikely that laws would be violated, but I do not see how the conservation of momentum is achieved in this situation. Even if the total momentum is conserved by considering the momentum of the magnetic field, if any, it would not seem to prevent the apparatus from being a reactionless drive for practical purposes, since I do not believe that any momentum of the magnetic field would be of concern for the purpose. The object of the reactionless drive is to move the apparatus through empty space.

Mike

 

[Vanadium 50]

Electric and magnetic fields are EM fields.

Thread closed.

 

[PJC01]

, this phenomenon is known as the homopolar motor and it is not a reactionless drive. While it may seem like there is no reaction to the force being applied to the magnet, there is actually a reaction occurring in the form of a torque on the magnet. This torque is caused by the interaction between the magnetic field and the electric current, and it follows Newton's third law of motion. The homopolar motor may not have a traditional propellant, but it still follows the fundamental laws of physics. Additionally, it is important to note that this is not a perpetual motion machine and the magnet will eventually come to a stop due to the dissipation of energy.