Lecture on Magnets and Electromagnetism

Introduction

• Magnetic properties known for thousands of years.
• Magnets used for navigation (e.g., compass) and practical applications (e.g., fridges).
• Recognizable types: Horseshoe magnets, bar magnets.

Basic Properties of Magnets

• Poles: North and South poles.
  • A bar magnet aligns with Earth's cardinal directions.
  • Like poles repel; opposite poles attract, similar to electric charges.
  • Difference: opposite charges can be isolated; magnetic poles cannot.

Understanding Magnetic Properties

• Requires knowledge of electron configurations and chemistry.
• Most materials: electrons paired with opposing spins, cancelling out magnetism.
• Ferromagnetism:
  • Materials like iron, cobalt, nickel have unpaired electrons.
  • Atoms align spins in parallel, forming magnetic domains and generating magnetic fields.

Magnetic Fields

• Represented by field lines:
  • Appear to start at the north pole and end at the south.
  • Form closed loops through the magnet.

Earth as a Magnet

• Earth is a giant bar magnet.
• Magnetic poles differ from geographical poles due to the Earth's iron core.
• Magnetic poles move slightly over millennia.
• Earth's magnetic field interacts with solar charged particles:
  • Produces aurora borealis.
  • Protects Earth from harmful radiation.

Relationship Between Electricity and Magnetism

• Electric current affects compasses; magnetic fields influence charged particles.
• Electromagnetic Force:
  • Unites electricity and magnetism.
  • Right-hand rule: Thumb direction = current, fingers = magnetic field.

Electromagnetic Waves

• Fluctuations of electric and magnetic fields generate electromagnetic waves.
• Historic unification of forces in physics.
• Goal of physics: unify all fundamental forces (Grand Unified Theory).

Transition to Modern Physics

• 20th century: New discoveries by Einstein and others.
• Dual nature of particles and waves.
• Variability of time and curvature of space.

Conclusion

• Encouragement to explore further in modern physics courses.
• Call to action for subscriptions and support.