The second, though, happens whenever we have an electric charge that's physically moving through space moving charges make currents, and electric currents induce magnetic fields. The first is from the inherent angular momentum, or spin, of a particle, like we have for the electron. There are two ways that nature can make a magnetic moment.
![is there anything smaller than a quark is there anything smaller than a quark](https://physicsworld.com/wp-content/uploads/2010/01/quark1.jpg)
Things make a lot more sense if you consider the possibility that the proton and neutron aren’t themselves fundamental, point-like particles, but rather are composite particles made up of multiple charged components. Instead, the proton’s magnetic moment is almost three times as large as that naive expectation, while the neutron’s magnetic moment is about two-thirds of the proton’s value, but with the opposite sign. Similarly, because the neutron is neutral, you might expect its magnetic moment is zero.īut that’s not what nature gives us at all, and that’s a major clue that the proton and neutron aren’t fundamental. You might think, then, that if you just replace the mass of the electron with the mass of the proton, and flipped the sign (from the opposite electric charge), you’d get the proton’s magnetic moment. So you might think, then, what if we measured the magnetic moment of the proton and the electron? Particles can have an intrinsic angular momentum to them - known as spin - and an electron, being a fundamental particle with no internal structure, has a magnetic moment that’s directly proportional to its charge, mass, the speed of light, and Planck’s constant. The reason? The proton’s charge is equal and opposite to the electron’s charge. If you did the exact same experiment, but with a proton instead of an electron, you’d get a force that was equal-and-opposite to the force the charged particle experienced in the first experiment. If you take a charged particle and bring it close to an electron, the electron will either attract or repel it with a specific force (the electrostatic force) that’s directly related to only two things: the particle’s electric charge and its distance from the electron.