PhysicsLAB Lab
Forces Between Ceramic Magnets

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The purpose of this experiment is to investigate the strength of the magnetic field between two circular, ceramic washers by placing washers on top of a "floating magnet" and recording the distance of the gap between it and two stationary magnets. The magnetic field of an ideal dipole can be calculated with the equation:
where µo is the permeability of free space and µ is its magnetic moment. For the purposes of our experiment, we are not investigating the values of these constants, but whether we can replicated the relationship that Baxis is proportional to 1/d3.
Each group will be provided with the following equipment:
  • three round ceramic magnets with 3/8" diameter holes
  • 32 washers
  • one aluminum rod with a 3/8" diameter
  • one test-tube clamp
  • one ring-stand
  • one c-clamp
  • one triple beam balance
  • one centimeter ruler
Carefully set up your equipment as shown in the example station. Make sure that you treat the magnets with respect. Their domains can be damaged if they are dropped or handled carelessly. Also keep these magnets AWAY from electronic devices as permanent damage will most likely occur. These magnets are strong.
Begin by measuring the mass of a single magnet which will "float" above the other two. Then mass all 32 washers and obtain an average mass for one washer.
Next "float" the single magnet above the other two aligned magnets. Carefully place all 32 washers on top of the "floating" magnet and record the distance separating the two sets of magnets. Then, in groups of 4, remove the washers and continue to record the separation distance. When all washers have been removed, again record the separation between the two sets of magnets.
Repeat the process TWO additional times, resulting in a total of three trials of measurements. Fill in your values in the chart below.
Data Table
After all of your data has been collected, graph your results using the spreadsheet 1-ceramicmagnets.xls. Each round will be represented by a separate trend line on the first graph of Mass vs Gap Distance.
Analysis and Conclusions
What was the average mass of one washer (g)? 

What was the mass of the floating magnet (g)? 

Based on your R2 values, which round of trials had the best results for the graph Mass vs Gap Distance?

What was EXCEL's regression equation for this round of trials?

What was EXCEL's regression equation for your graph of Weight vs 1/(Av Distance)3?

Within the "linear portion" of your graph of Weight vs 1/(Av Distance)3, compare the distances supporting the weight with 4 washers and the weight with 20 washers.
washers weight distance
Based on your products: W4*(d4)3 and W20*(d20)3, would it be appropriate to say that your experiment supported the hypothesis:
"the magnetic force between two magnets is inversely proportional to the cube of the distance between the magnets"?
Answer yes or no as well as explain your rationale.

Adapted from:

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Catharine H. Colwell
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