MadSci Network: Physics |
Several physics terms are confused here. Electromagnetic fields act on
electrical
charges. The electromagnetic force is the amount of force exerted on
a charge by the fields present. Electromagnetic radiation is a mixture
of electric and
magnetic fields. An electric field can be conceptually viewed as an
extended volume of
space in which electric field energy is present. This field is created
by electric charges or
by changing magnetic fields, and it exerts a force on any charges
present. At any point
the field has a particular direction. We can visualize this by drawing
lines (commonly called
"field lines") along the direction that small charges would move if
placed in the field.
A magnetic field is similar. Since no one has ever observed magnetic "charges"
we say that a magnetic field is created by the motion of electric charges or
changing electrical
fields. It exerts a force on moving electrical charges perpendicular to
their motion and
perpendicular to the magnetic field lines (similar to the electric
field lines). For example,
if the motion of a particle is along the x-axis and the field is along
the y-axis, then the
force is along the z-axis in a direction determined by something called
the "right hand
rule." Any textbook on physics can explain these phenomena in much
greater detail.
Electromagnetic radiation comes in photons. A photon is an alternating
electromagnetic
field. Since changing electric fields can create magnetic fields, and
vice versa, the
photon exists by constantly exchanging its energy back and forth
between the two in
a wave. Because of its quantum nature, photons can only be absorbed or
emitted as
whole units. For further reading on that subject, search the web for
"photoelectric
effect" on any search engine.
Lastly, for the attraction or repulsion between charged particles, all
charges create an
electric field. Another charge in that field will want to move along
the field lines,
either towards or away from the particle that created the field. What
makes the particles
in the field move is the force (the electromagnetic force) that the
field exerts on the
charges themselves. The first particle will feel an equal and opposite
(in direction)
force from the second charged particle, which is also creating an
electric field.
Charged particles feel no force from their own electric fields. This is
also explained
in greater detail in any physics textbook, with many colorful
illustrations.
For a neat program that lets you place charges and draw the associated
fields, as well
as links to the basic theory of electromagnetic fields and forces click here.
Try the links in the MadSci Library for more information on Physics.