Fundamentals of Magnetism and Magnetic Materials

Magnetism: Historical Origins

Magnetism: One of the oldest phenomena known for thousands of years, corresponding to mineral deposits of magnets called magnetite.

Discovery

Discovery: The Chinese were likely the discoverers of terrestrial magnetism, resulting from the technological invention of the compass.

Magnetic Phenomena

Magnetic Phenomena: Scientific study began centuries ago; in 1820, it was discovered that electric currents give rise to magnetic effects.

Properties of Magnets

Magnets are composed of a material called magnetite, which has the property of attracting iron; this property is called magnetism.

Classification of Magnetic Materials

• Paramagnetism: Bodies with easily orientable magnetic domains that are simple to magnetize.
• Diamagnetism: Materials that are difficult to magnetize or cannot be magnetized.
• Ferromagnetic materials: Materials such as iron, cobalt, and nickel, which are strongly paramagnetic.

Types of Magnets

• Alnico: Produced by fusion and synthesis.
• Ferrite: Made of barium and strontium.
• Rare Earths: Metal materials with a force 6 to 10 times greater than traditional magnetic materials.

Characteristics of Magnets

Magnets possess a north pole and a south pole. These can be identified with a simple compass, bearing in mind that the compass needle points toward the magnetic north pole of the Earth.

Permanent Magnet Polarity

You can suspend a magnet from a fine thread so that it can rotate freely to orient itself to the Earth's magnetic field.

Electromagnetism and Theory

Electrical Theory of Magnetism

In 1820, a Danish physicist observed that a magnetic needle oriented in a particular direction in the vicinity of a wire carrying an electric current. He observed that the effects of these experiments could divert a magnetic compass.

Magnetic Field and Force

Magnetic Field: The region of space in which magnetic phenomena are manifested.

Magnetic Force: Changes the velocity but not the magnitude of the charge; therefore, it does no work.

Formula: F = qvB sin(θ)

Where q is the electric charge, v is the velocity, B is the magnetic field vector, and θ (theta) is the angle between the velocity vector and the magnetic field vector.

Magnetic Instruments and Devices

Measurement Tools

• Galvanometer: A transducer that produces a needle rotation in response to electric current flowing through its coil.
• Voltmeter: An instrument used to measure the potential difference between two points of an electrical circuit.
• Ammeter: An instrument used to measure the intensity of current flowing through an electrical circuit.

Advanced Applications

• Cyclotron: A particle accelerator built by Ernest Lawrence and M. Stanley Livingston at Berkeley in 1939.
• Cathode Ray Tubes: A display device invented by William Crookes in 1875.