# Lorentz force in homopolar motor

There are a lot of videos showing the simple homopolar motors in action. Let's look at this one: http://www.youtube.com/watch?v=6jyraFLqfqE It is supposed to be working due to the Lorentz force.

Electrons go through the magnet, deflect under magnetic field due to the Lorentz force and colliding with atoms in the magnet, rotate it.

But what if electrons would travel not through the magnet itself but through the thin wire put between the battery and the magnet, directly connecting + and - of the battery. In this way electrons would still travel in the same direction in same magnetic field, but in the thin wire, not in the magnet. Would then the magnet rotate?

Now the other video: http://www.youtube.com/watch?NR=1&v=zOdboRYf1hM&feature=fvwp Here electrons travel through the wire but still close to the magnet so we still can assume that electrons are deflected due to the Lorentz force even though magnetic field should be weaker on the side of the magnet.

But what would happen if everything would be glued together: battery, magnet, wire. Would then this system rotate? While the electrons would still travel under the magnetic field they should be deflected and rotate the whole system. But it sounds unphysical. Can somebody explain how it works?

• If the whole thing was levitating, I don't see why it couldn't rotate. Its simply a device that transfers electric potential energy (the battery) into kinetic rotational energy. It doesn't rotate for 'free', it needs to battery's energy. This is no different from a bomb being able to explode on its own. Transfer some inner potential energy to whatever, by whatever mechanism. In this case the device is made such to provide the magnetic scaffoldings to make itself spin with Lorentz force Commented Jul 14, 2013 at 22:09

Just to clarify, electrons do not go through the magnet. The coating or enamel of the magnet is a conductor and the wire touching the enamel of the magnet closes the circuit as the electrons will travel the around the magnet. As you probably know, current generates a electromagnetic field and the interaction of the electromagnetic field and magnetic field of the magnets is causing the rotation. Hence, there is no motion due to "electrons hitting the magnet's atoms".

Would the magnet rotate if the wires are connected directly between the + and - pole? assuming you don't short the circuit (which you will), and the electromagnetic field F is strong enough to interact with the magnet's field B, then yes, it would rotate.

As far the apparatus achieving an angular momentum when all parts are glued together the answer is no, it wouldn't. The reason that you have motion on both videos that you posted is that at least one of the parts that has a magnetic (B) or electromagnetic (F) field is free to rotate, otherwise the repulsion forces between the charges would null each other. It is like trying to open a chest door with your both feet on the top. You are not opening that chest, my friend. click here to see a representation of the homopolar motor. That will give you good idea of how the electromagnetic field and magnetic field interacts.

If everything is glued together the magnetic fields of moving charge and magnet would still interact. The magnetic fields would attract and condense on one side of the charge and expand on the other side creating the Lorentz force. The condensing and expanding of the magnetic fields creates a warp in space that gravitates both mass and charge together in one direction as in Einstein's gravitation theory but the space warp acts as a moving wave that deflects both the moving charge and the magnetic mass together.

• This is still gibberish. Nothing in this problem causes space to warp. Commented Jul 14, 2017 at 21:51

The conical magnetic field of a moving charge attracts a external uniform magnetic field condensing both fields on one side of charge and expanding both fields on the opposite side creating a warp bubble in the eather causing a force to gravitate the charge direection to one side of its foward movement taking along the external magnetic field mass resulting in Lorentz force action on charge and mass. The presence of a external uniform magnetic field acts only on the magnetic field of the moving charge which moves by electric or kenetic action resulting in current or mechanical force. The movement of a uniform magnetic field has no effect on a stationary charge since no conical magnetic field of the charge is created by movement of charge through the eather. Thus both the uniform magnetic field external to charge can move together with the charge to create a current since the conical magnetic field of charge warps the external magnetic field moving with the charge.

• I'm pretty sure this is gibberish, and I'm pretty sure it doesn't remotely answer the question Commented Jul 14, 2013 at 22:15