Atoms and Magnetism

The Source of Magnetism

The origin of magnetism is a very complicated concept. In fact, there are some details about magnetism on the atomic scale that scientists still do not fully agree on. To begin to understand where magnetism originates and why some materials can be magnetized while others cannot, requires a fair amount of quantum theory. Quantum theory is the study of the jumps from one energy level to another as it relates to the structure and behavior of atoms. However, explaining quantum theory is well beyond the scope of this material, so this subject will be reserved for college chemistry and physics classes. Nevertheless, the basic scientific principles of magnetism can be explained if a few generalizations and simplifications are made.

Recall that all matter is composed of atoms, and atoms are composed of protons, neutrons and electrons. The protons and neutrons are located in the atom's nucleus and the electrons are in constant motion around the nucleus. Electrons carry a negative electrical charge and produce a magnetic field as they move through space. A magnetic field is produced whenever an electrical charge is in motion. The strength of this field is called the magnetic moment. 

This may be hard to visualize on a subatomic scale but consider electric current flowing through a conductor. When the electrons (electric current) are flowing through the conductor, a magnetic field forms around the conductor. The magnetic field can be detected using a compass, like was shown on the previous page. The magnetic field will place a force on the compass needle, which is another example of a dipole.

Since all matter is comprised of atoms, all materials are affected in some way by a magnetic field. However, not all materials react the same way. This will be explored more in the following pages.

The study of atoms, electrons, neutrons, and protons is so complex that throughout history scientists have developed several models of the atom. From the early Greek concept of the atom, about 2400 years ago, to today's modern atomic model, scientists have built on and modified existing models, as new information was discovered. There are still concepts on which scientists do not fully agree. In an attempt to simplify the concept and describe how some materials become magnetized, we are using a simplification of the Niels Bohr Model of the atom. In his 1913 model Bohr depicted electrons spinning and orbiting the nucleus of an atom. The direction of spin and orbit of the electron determines the direction of the magnetic field.

In our exercise, the electron appears to orbit in the same path around the nucleus, but electrons do not really orbit in the same path.  They change their path with each revolution and are commonly described as existing in clouds that surround the nucleus of an atom. Because electrons move so quickly, it is impossible to see where they are at a specific moment in time. 

In the early 1800s, A. M. Ampere first suggested the theory that magnetic fields were due to electric currents continually circulating within the atom.  Ampere's insight was pretty amazing considering the electron would not be discovered for another 75 years.