Lesson 38: Properties of Magnets
Magnets attract some materials and have poles that can attract or repel each other. This lesson covers magnetic materials, natural and manufactured magnets, and the effects of distance on magnetic force.
Key Ideas
- Only a few metals are magnetic: iron, nickel, cobalt, and steel (which is mostly iron). Most metals, like aluminum and copper, are not.
- Magnetism was first discovered in nature, in a naturally magnetic rock called lodestone, before people learned to make magnets themselves.
- Every magnet has two poles, North and South. Opposite poles attract and matching poles repel, no matter the magnet's shape.
- A magnet's force can act without touching, and can pass through materials like paper, plastic, and glass, but it fades with distance.
- Magnets can be temporary, like a rubbed paperclip that loses its pull, or permanent, like a store-bought magnet that holds its pull for years.
- Magnets vary hugely in strength depending on what they're made of, and they do real jobs all around us, from cranes to speakers.
Vocabulary
- Magnet: An object that produces a force pulling on iron, nickel, cobalt, and steel, without needing to touch them.
- Pole: One of the two ends of a magnet, called North and South, where the magnetic force is strongest.
- Attract: To pull toward. Opposite magnetic poles attract each other.
- Repel: To push away. Matching magnetic poles repel each other.
- Lodestone: A naturally occurring magnetic rock, found already able to attract iron without being made by anyone.
- Permanent magnet: A magnet, usually made of a special metal alloy, that holds its magnetism for years without fading.
Discussion Questions
- A friend says a magnet sticks to anything metal. Using what you tested at home, what's wrong with that claim?
- You have a rubbed paperclip and a store-bought magnet, both able to lift another paperclip right now. Predict which one will still work in a month, and why.
- You hold two magnets a finger's width apart and feel a pull before they even touch. What does that tell you about how far a magnet's force can reach?
Supplies
- A magnet, or two different magnets if you have them
- A handful of paperclips, a coin, aluminum foil, and other household objects to test
- A sheet of paper