Fundamental Concepts of Magnetism and Electromagnetism

Concepts and Electromagnetic Phenomena

Magnetic Field Definition

Magnetic Field: The area which shows the effects of magnetic poles is said to have a magnetic field. A magnetic field is represented by lines of force.

Magnetism: Lines of force of a magnetic field created by a permanent magnet.

Magnets

• Magnets attract or repel each other, similar to electric charges.

Magnetic Magnitudes

Magnetic Flux Density (B): The number of magnetic field lines that cross the unit area (m²).

• Magnetic Flux (Φ)
• Magnetic Field Strength (H)

Electromagnetism

Electromagnetism involves the creation of a magnetic field through an electric current, or the creation of an electrical current in the presence of a magnetic field.

Biot-Savart Law

An electrical charge (q), which moves with velocity (v), creates a magnetic field (B) at a point (P) located at a distance (r).

Magnetic Flux (Φ): The total number of lines of force passing through a surface. Measured in Webers (Wb).

Magnetic Induction

The relationship between the magnetic induction or flux density (B) and the magnetic field strength (H).

When bringing a magnet near a conducting loop that is not connected to any power source, a galvanometer detects a current while the magnet is in motion relative to the loop.

• The direction of the induced current when bringing the magnet closer is opposite to the direction when the magnet is removed.
• If the magnet is fixed and the loop moves, the result is the same.

This indicates that an electromotive force (EMF) is produced in the circuit, leading to the current. This phenomenon is called Electromagnetic Induction.

E = B l v (Motional Electromotive Force)

Faraday's Law of Induction

The absolute value of the induced electromotive force (EMF) is defined by the rate of change of magnetic flux (Φ).

Lenz's Law

The induced electromotive force must be such that it tends to establish a current whose magnetic field opposes the change in magnetic flux that produces it.

Magnetic Properties of Matter

Diamagnetic Materials

Diamagnetic: Materials whose induced magnetic fields are opposed to the external applied field.

• Gold: 0.999964
• Silver: 0.99998
• Copper: 0.999991

Paramagnetic Materials

Paramagnetic: Materials exhibiting a magnetization that tends to slightly increase the external applied field.

• Vacuum: 1
• Air: 1.00000036
• Aluminum: 1.000021
• Tungsten: 1.000068
• Palladium: 1.00082

Ferromagnetic Materials

Ferromagnetic: Materials characterized by forming Weiss domains or zones.

• Cobalt: 250
• Nickel: 600
• Commercial Iron: 6000

Permeability Definitions

• μ₀: Permeability of vacuum.
• μ_r: Relative permeability of the material.
• μ: Absolute permeability.