Applied Science - Physics (4B)
Pre Lab 

   
OBJECTIVES:
  • Exploring magnetism.
  • Making a magnet.

VOCABULARY:

  • attract
  • magnetism
  • north
  • repel
  • south
MATERIALS:

Students made a magnet with a hammer and piece of steel.

BACKGROUND:

A Medieval seaman's code declares that any sailor caught tampering with the ships lodestone ".....shall, if his life be spared, be punished by having the hand which he most uses, be cut and fastened by a dagger or knife thrust through it, to the mast or principal timber of the ship....." In the history of science, this strict code is vivid evidence of human's early dependence upon magnetism. Lodestone was used for navigational purposes in a compass and without a compass, captains could not find north.

Explain that a magnet has a north pole and a south pole. North and south will attract, but "like" poles will repel each other. Magnetism is created when electrons "spin" in the same direction. In some substances this occurs naturally, but in most substances it does not. Items can be magnetized by hitting them so that all the electrons "spin" in the same direction.

The Earth acts as a huge magnet. As a result, pieces of iron or steel which lie in a North - South direction often became magnetized by "induction." Induction means the "forcing" of an object. If such objects are jolted while in this position, their molecules line up and they become more easily magnetized. Thus, some materials can be magnetized by tapping them with a hammer.

PROCEDURE:

  1. Gently tap one end of an iron rod or bolt about 20 times while holding it in a North - South position. Then try to pick up some iron files. Best results are obtained if the rod is located along the earth's magnetic lines of force. Since we are in the Northern Hemisphere, tilt the north end of the rod downward. It may be necessary to try various angles of inclination before the rod is properly aligned with the Earth's magnetic line of force. If you live near a railroad track, a discarded iron tie works great.
      
  2. Try this experiment with your students and see if it works. Sometimes it sounds easier than it is and conditions have to be ideal. Some students will get it to work, others won't. Have the students try and figure out why it did or didn't work. Have students experiment at home under supervision. Make sure they hammer the piece of iron, and not their fingers!
      
  3. You may want students to present the information they researched in the Post Lab.

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