[Nexus 4 Q&A, Help & Troubleshooting] USSENTERNCC1701E:
Let's start with how to calculate the force on a charged particle due to a magnetic field. F=qv×B. Where q is the charge on the particle, v is the particles velocity, and B is the magnetic field strength where the particle is. Those familiar with cross products know we can calculate the magnitude of this force with (qvB)sin(θ), where theta is the angle in between the direction of the field and the direction of the particles velocity. So if the magnetic field and the particles velocity are in the same direction, theta is zero, and since sine of zero is zero, there is no force due to the magnetic field on the object. How then is it that a magnet makes an object move straight at it, in the same direction as the magnetic field? One could say that there is also an electric field from the magnet that is causing the force, but I tell you this is not the case. Why not? This will delve a little into relativity. Lets say we are charged particles moving through a magnetic field perpendicular to the field direction. We feel a force and can determine that there is a magnetic field. But what if we are not moving relative to the field. Going back to that equation, we feel no force if we have no velocity, so in our reference frame, there is no magnetic field. Now what if in our stationary frame we look at a particle that is moving relative to us, we see that particle is accelerating, but there is no magnetic field, why is it moving. It turns out there is an electric field in our reference frame that produces exactly the same force on this particle we are looking at, as the magnetic field in that particles reference frame produces. So the electric and magnetic field strengths actually depend on your motion relative to the field, and they are intimately coupled such that from any reference frame the force applied to a particle looks the same. Now, back to why I say there is no electric field in our first example. Simply because I can, earlier I showed there is a situation where there is no magnetic field and only electric, there can also be a reference frame where there is no electric field and all magnetic. That's where we are now. So, this object starts moving slowly directly toward a magnet, it's velocity is in the same direction as the magnetic field, so the magnetic field does not apply a force to it, and we are in such a reference frame that there is no electric field from the magnet. But the object accelerates, there must be some force on it, and it is not an electric force from the magnet. The answer lies in the atomic structure of the object. At any given time there is almost certainly some electron flying around through the material, NOT parallel to the magnetic field. (Side note: this is why only certain materials respond to magnets, the electrons must be free to flow from atom to atom). The magnetic field accelerates these electrons (creating electric charge imbalances within the metal). The electrons in turn accelerate the nuclei with electric fields, because they are moving relative to us, we can't say they never generate their own electric fields.

So, a magnet accelerates the electrons in certain metals, those electrons then create electric fields which accelerates the protons in the metal's nuclei, but no electric field actually comes from the magnet.

And that's how magnets work!

---------- Post added at 01:17 PM ---------- Previous post was at 01:17 PM ----------

Any questions, let me know :D