Wednesday, January 6, 2010

Physics: Making magnets

A couple weeks back the kids discovered that iron-containing metals can themselves become magnets if they are rubbed by a magnet. We used this observation to build compasses in 3 easy steps:
  1. Rub a light-weight iron needle with a magnet (always in the same direction) 50 times.
  2. Stick it through a thin piece of Styrofoam.
  3. Set the whole business afloat in a bowl of water and observe how try as you might, you cannot prevent the needle from pointing along a north-south axis.

Afterward, the kids built electromagnets. In an electric circuit, the movement of electrons creates a magnetic field, but because it is so weak, you might not notice it. However, if you build a circuit with MANY loops of wire, all in the same direction, each loop reinforces the strength of the magnetic field.

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