Overview
This lecture covers different ways magnets are classified, focusing on their origin (natural or artificial) and how long they retain magnetism (permanent or temporary).
Shapes of Magnets
- Bar, horseshoe, cylindrical, ring, and spherical magnets are different shapes, not types.
Classification by Occurrence
- Magnets are classified as naturally occurring or artificial (manmade).
- Lodestone is the strongest and best-known natural magnet.
- Other natural magnetic materials include pyrrhotite, columbite, and basalt (less magnetic than lodestone).
- Most everyday magnets are artificial.
Classification by Duration of Magnetism
- Magnets are classified as permanent or temporary based on how long they retain magnetism.
- Permanent magnets retain their magnetism even without an external magnetic field.
- Temporary magnets only act as magnets when in a strong magnetic field.
Key Relationships
- All naturally occurring magnets are permanent magnets.
Key Terms & Definitions
- Naturally Occurring Magnet — a magnet found in nature, such as lodestone.
- Artificial Magnet — a manmade magnet, commonly used in daily life.
- Permanent Magnet — a magnet that retains its magnetic properties without an external field.
- Temporary Magnet — a magnet that loses its magnetism once the external magnetic field is removed.
Action Items / Next Steps
- Review definitions and classifications of magnets.
- Prepare to learn more about how permanent and temporary magnets work in upcoming lessons.