Attractive and repulsive Magnetic force

• Magnetic forces
• Magnetic poles

In physics, magnetism is one of the forces in which materials and moving charged particles exert attractive, repulsive force or moments on other materials or charged particles. Some well-known materials that exhibit easily detectable magnetic properties (called magnets) are nickel, iron, cobalt, gadolinium and their alloys; however, all materials are influenced to a greater or lesser degree by the presence of a magnetic field. Substances which are negligibly affected by magnetic fields are known as non-magnetic substances. They include copper, aluminum, water, and gases.

Magnetism also has other definitions and descriptions in physics, particularly as one of the two components of electromagnetic waves such as light.

Just like when the Greeks of the old times discovered the first naturally occurring magnetic stones, or natural magnets, you have been observing a property of matter called magnetism. Magnetism is the force of attraction or repulsion in a material. Certain materials such as iron, steel, nickel, or magnetite exhibit this force while most other materials do not.

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 high school and college chemistry and physics classes. The basic scientific principles of magnetism can be explained, nevertheless, a few generalizations and simplifications are made.

First, you must recall that all matter is made up of atoms. Atoms have a positively charged center called the nucleus. A nucleus contains one or more protons and neutrons and is orbited by one or more negatively charged particles called electrons. A simplified animation of the center of an atom is what you observed. You should have concluded that the electrons spin as they orbit the nucleus (which contains protons and neutrons) much like the earth spins as it orbits the sun. As the electrons spin and orbit the nucleus, they produce a magnetic field. A. M. Ampere first suggested the theory that magnetic fields were due to electric currents continually circulating within the atom in the early 1800s. Ampere's insight was pretty amazing considering it was not known for sure whether atoms existed in the early 1800s and the electron would not be discovered for another 75 years.

What is a magnetic field and how is it created?

A magnetic field describes a volume of space where there is a change in energy. Later, you will see a simple way to detect a magnetic field with a compass. As Ampere suggested, a magnetic field is produced whenever an electrical charge is in motion. The spinning and orbiting of the nucleus of an atom produces a magnetic field as does electrical current flowing through a wire. The direction of the spin and orbit determine the direction of the magnetic field. The strength of this field is called the magnetic moment.

The motion of an electric charge producing a magnetic field is an essential concept in understanding magnetism. The magnetic moment of an atom can be the result of the electron's spin, which is the electron orbital motion and a change in the orbital motion of the electrons caused by an applied magnetic field.

• Plastic Cased Bar Magnets — 4611.40