Magnetism

Magnetism has similar properties to electricity, however they are not the same.  The first evidence of this is that a magnet has two poles.  They, always, have a north and south pole.  This is in opposition to electricity, which can have a single charge (positive or negative).  Exploring the properties of magnetism (and electricity) can lead us to a relationship that exists between magnetism and electricity, which will be our theory of electromagnetism. 

            A magnet can be viewed as possessing a “single property” divided in two parts.  The “single property” is that a magnet is always a dipole.  This means that it will always have two parts: a north pole and a south pole.  Analogous to electricity, same poles will repel and opposite poles will attract.  Also analogous to electricity, magnets can also attract neutral objects, but not all.  If one pole of the magnet attracts the object, so will the other pole of the magnet.¹  The magnetic field exists as one of the properties of magnets.

            The magnetic field emerges from the north pole and enters the south pole.  This field exists everywhere in space around the magnet.  An example of a magnet field is the field that surrounds the Earth.  The Earth’s magnetic field protects us from incoming particles from the sun (as well as other stuff).  This also produces the aurora seen at the geographic poles.  The aurora forms as charged particles spin around the magnetic field toward the poles.²  These charged particles excite atoms in the atmosphere and create the colors associated with the aurora.  

Let’s consider the magnetic field that forms around a current carrying wire.  This means that a magnetic field exists because a wire has moving charges within it.  The magnetic field can be visualized as a circles around the wire.  The circles have no beginning and no end.  We can imagine a number of concentric circles coming out of the wire.³  This is a magnetic field that exists everywhere and interacts with its environment.

A magnetic field can also be created by a changing electric field.  This is known as the induced magnetic field.  This can be thought of much like the induced electric field.⁴  This field can be visualized like the one in a current carrying wire, as described above.

The magnetic field has one more important property.  That is, an electric charge moving in a magnetic field has a magnetic force exerted on it.  This is known as the Lorentz force.⁵  This is the last fact we need about magnetism before proceeding to a complete conceptual definition of electromagnetism.