kashiark said:
If an electric field causes 2 previously stationary charges to accelerate(let's say that there was something inhibiting their movement that has now been removed) toward or away from one another, what type of field is between them, electric or magnetic?
Rather than "between" I'll say 'around' each moving electric charge there will be one electric field and three magnetic fields.
1x Electric field, described with Coulomb's law:
1x Magnetic field 'due to moving charge', described with Biot-Savart law:
2x Magnetic fields 'due to spinning charge', described with magnetic dipole equation:
However, the magnetic field 'due to moving charge', the one most important here, in the case when electrons are orbiting nucleus will describe doughnut shaped magnetic field whose superposition through time will actually form a dipole moment, so in total there would be four magnetic fields and one electric field around an electron circling a proton. This 'doughnut' or "compound magnetic field" due to electron circular orbit around nucleus will create two opposite magnetic fields, above and below the ring. This dipole moment is what is responsible for magnetism in permanent magnets, not the magnetic dipole moment due to electron spin, or so they say.
Ok, let's say we have a positron and an electron moving toward one another; which way would the magnetic field point? Does it depend on their spins? If so, what if they have the same spin?
Use Lorentz force and Biot-Savart law to calculate their motion and the forces of attraction and repulsion to know which way will they move. Two parallel wires attract if they carry current in the same direction and they repel if the current goes in opposite direction.
So, considering only this magnetic field described by Biot-Savart law, if two electrons passing each other in opposite directions repel, that means positron and electron moving toward one another will ATTRACT.
However, if you further model this interaction you will find they will attract and repel depending on their position, velocity and relative orientation, in other words they will continue oscillate around each other, if they come close enough. You could say they will form an electric dipole which due to superposition principle might appear as having zero electric charge... these two particles interacting together would look a lot like a photon or em radiation.
Actually, in the process called 'Pair_production' photons will "split" in electron-positron pairs and in the opposite process called 'Positron-electron_annihilation', these two types of particles form photons or em radiation.
Isn't the magnetic moment of an electron (and positron for that matter) dependent on the spin? And isn't the magnetic field dependent on the magnetic moment?
There is that, which is usually called "magnetic dipole moment due to intrinsic spin", and there is the one described with Biot-Savart law and is called "magnetic field due to moving charge". Later one apperantly have much greater influence and is responsible for magnetism in permanent magnets, the magnetic dipole moment due to spin kind of cancels itself out since it has two opposite fields close together, or so it would seem.
