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Straight Through: Can Magnetic Forces Act Through Paper?

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Author: Janice VanCleave

Problem

Can magnetic forces act through paper?

Materials

  • sheet of paper
  • bar magnet
  • thumbtack

Procedure

  1. Lay the sheet of paper on a wooden table.
  2. Place the magnet so that its north pole is under the edge of the paper.
  3. Position the tack on top of the paper where the paper covers the end of the magnet.
  4. Hold the uncovered end of the magnet with your hand and move the magnet from side to side under the paper.

Results

The paper is not attracted to the magnet, but the tack is. Moving the magnet caused the tack to move.

Why?

Around every magnet is an invisible magnetic force field. Some materials, such as paper, do not stop or disrupt the pattern of the force field. Materials that allow a magnetic force field to pass through without any disruptions in the magnetic field are said to be nonpermeable. Materials that seem to absorb the magnetic lines of force are said to be permeable. Nonpermeable materials are not attracted to a magnet, whereas permeable materials are attracted to a magnet. The magnetic field passes through the paper with no change in the direction of the field; thus, the paper is nonpermeable and nonmagnetic. The magnetic field moves in and around the tack; thus, the tack is said to be permeable to the magnetic field.

Straight Through

Let's Explore

  1. Do both ends of the magnet behave the same way? Repeat the experiment, turning the magnet around so that its south pole is under the edge of the paper.
  2. Would thicker paper allow the magnetic field to pass through? Repeat the experiment twice, replacing the sheet of paper with thicker paper and with cardboard. Science Fair Hint: Photographs taken during each testing and diagrams with labels describing the procedure can be used as part of a project display along with paper samples.
  3. Do materials other than paper allow magnetic force lines to pass through?
  4. Straight Through

    Repeat the original experiment, replacing the paper with different materials, such as wax paper, aluminum foil, plastic wrap, a cookie sheet, a metal cake-server, or a glass bowl. Science Fair Hint: Record and use your results as part of a project display along with the samples tested.

Show Time!

  1. To compare the strength of two different-sized magnets, place one magnet under a few pages of a book. Place a paper clip on top of the pages, so that the paper clip is attracted by the magnet. Start putting more and more pages between the magnet and the paper clip until the paper clip is no longer attracted to the magnet. Now replace the first magnet with the second magnet, and repeat the procedure to compare the number of pages through which each magnet is able to attract the paper clip. The results of this experiment can be displayed along with diagrams and/or photographs.
  2. Straight Through

  3. To test the non permeability of liquids, pour a clear liquid such as water or com syrup into a glass. Place a magnet inside a plastic bag and tie a string around the top of the bag. Stir iron filings into the liquid and quickly lower the plastic bag into the liquid. Make and display drawings of the procedure and results.

Check It Out!

What is in the magnetic force field that passes through nonpermeable material but is absorbed by permeable material? Some scientists think that invisible particles called magnetic monopoles fly out of the north pole of a magnet, loop around the magnet, and then fly back into the south pole of the magnet. Your parent, teacher, or librarian can assist you in finding information about magnetic force fields and about non permeable and permeable materials. When presenting these materials, use a poster showing examples of the two types of materials.

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