Why does an electric field generate a magnetic field, is it due to the fact that electrons have a spin and this spin generates it ? and why do magnets attract or repel each other, I mean as far as I know magnetism is generated due to the fact that electrons have a spin, so why do magnets have a tendency to align to other magnetic fields, why do they attract or repel each other?

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anonymous · Answer

@Reyzalex
The simplest explanation as to why magnetism in matter exists is due to the concept of spin but the reason for magnetic fields is found in the motion of charge.  Moving charges produce magnetic fields .   Classically the magnetic moment associated with spin can be explained by the rotation (motion)  of the charge of the electron assuming the electron is a sphere of charge.  But this is probably just a convenient model for the electron diameter is found to be much smaller than that derived from the classical model. 

A coil of wire carrying a current (electromagnets) has a magnetic moment and a magnetic field .  Electromagnets act like magnets or vice versa .   The interaction between magnets is "explained" as the effect of the magnetic field produced by one magnet on the magnetic moment of another magnets.  Magnetic moments are analogous to electric moments but have no reference to a "magnetic charge" although for convenience a magnetic charge can be formulated (called a Pole).  The why of attraction or repulsion comes down to the why of a magnetic or for that matter an electric field?  It is the nature of charges to have these properties at least as I currently understand the state of knowledge of electromagnetism.