Electromagnetism

Electromagnetism

Objectives

• Discuss the history and development of magnetism.

• Describe the nature of magnets.

• Identify ways of magnetizing and demagnetizing materials.

• Appreciate the importance of electromagnetism in daily life.

Electricity vs Magnetism

• Electricity: A form of energy resulting from the flow of charged particles (electrons).

  • Produces electrical current when electrons flow through a path called a circuit.

• Magnetism: Physical phenomena arising from the force caused by magnets.

  • The movement of electrons generates electricity, while a magnetic field results from electric currents.

Key Vocabulary

• Electromagnetic Induction: Process of using magnetic fields to produce voltage in closed circuits.

• Electromotive Force (emf): Another term for voltage.

• Magnetic Field: Area around a magnet where magnetic force exists.

• Magnetic Force: Attraction or repulsion between magnetic poles.

• Poles: The ends of a magnet (North and South).

• Electric Motor: Converts electricity to mechanical work.

• Electromagnet: Temporary magnet created by coiling wire around an iron core.

• Ferromagnet: Materials with strong attraction to magnetic fields.

• Ampere: Basic unit of electric current.

• Circuit: An electrical device that allows current to flow.

• Current: Flow of electricity through a conductor.

Historical Development of Magnetism

• Early Discoveries: Greeks referred to magnet materials as lodestones; the term magnet derives from the district Magnesia.

• Navigation: First use of magnets for navigation was by the Chinese as a compass.

• William Gilbert: First to artificially create a magnet; proposed that Earth has magnetic properties evident from compass behavior.

Important Figures and Discoveries

• Hans Christian Oersted (1820): Discovered that electric current produces a magnetic field.

• Michael Faraday (1821): Developed principles regarding electric motors following Oersted's discovery.

• Andre Marie Ampere: Suggested that electric current could exert a magnetic force, which implies that a current-carrying wire generates a magnetic field.

Types of Magnets

• Types of Magnets: Include bar magnets, ring magnets, horseshoe magnets, disc magnets, and magnetic needles.

Properties of Magnets

• All magnets possess both a North pole and a South pole.

• Like poles repel each other, while opposite poles attract.

• Magnetic poles cannot be isolated; no magnet exists with only one pole (no magnetic monopoles).

Magnetic Field

• Magnetic Field Characteristics:

  • The density of magnetic field lines indicates strength; closer lines indicate a stronger field.

  • Magnetic field lines emerge from the South pole and re-enter at the North pole.

  • Opposite poles attract leading to convergence of field lines, while like poles repel and separate field lines.

Northern Lights (Auroras)

• Occurs when solar wind penetrates Earth's magnetic field and collides with atmospheric particles.

• Energy from collisions (of solar wind ions with oxygen and nitrogen) produces the colorful auroras, termed Aurora Borealis in the north and Aurora Australis in the south.