Lesson 38
Properties of Magnets
We'll be testting which household objects a magnet actually grabs, discover that only iron, nickel, cobalt, and steel respond, and explore how magnets can be found in nature, made by rubbing a paperclip, and always come with two poles that either attract or repel.

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
  1. A friend says a magnet sticks to anything metal. Using what you tested at home, what's wrong with that claim?
  2. 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.
  3. 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