No Religion wrote:
> 1) A transformer and a system composed by a radio transmitter and a
>    radio receiver use the same underlying physical phenomena?

Define "same".  Given a unified field theory, just about everything is a
different manifestation of the same thing.  However, I will answer from a
more practical common usage EE point of view in which magnetic and electric
fields are separate things.  Maxwell's equations are probably the
appropriate level of detail in this context.

Given that, no, a transformer and radio communications over long distances
do not use the "same" physics.

> 2) Does magnetism really exist in itself, or is it just electricity
>    that manifests itself into a particular way? What is it (this way)?

Again given the view I described above, magnetic and electrical fields are
separate phenomena, although they are linked and interact.  Maxwell's
equations and the currently known laws of physics leave open the posibility
of magnetic monopoles, except that noone has actually ever found any.  If
they existed, they would give rise to static magnetic fields, just like
electrons and protons (electric monopoles) give rise to static electric
fields.  In the abscense of magnetic monopoles, the only way to create a
magnetic field is by electric current (moving electric charges).  By the
way, moving magnetic monopoles would create electric fields.

Even a "permanent magnet" creates its static magnetic field in this way.  In
this case the electric currents are the electrons spinning around the atoms
of the material.  Each electron going around in a circle creates a magnetic
field at right angles to the plane of the circle.  In most materials, the
spins are all independently and randomly oriented, so the fields from the
zillions of different orbiting electrons cancell out.  The unique property
of a permanent magnet is that there is a general trend in the alignment of
the electron orbits, giving rise to an aggregate magnetic field.

> 3) If an electrical static field starts changing (e.g. sinusoidally),
>    i.e. it stops being static, is it enough to call it an
>    electromagnetic field?

Yes, although the practicality of that statement depends on usage.  When we
talk about an "electromagnetic" field, we are usually interested in how it
propagates thru space.  Most of the time, this means we are talking about
some form of radiation, from low frequency radio waves on up.


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