The Effect of Temperature on Magnet Strength

Miyuki Blatt & Kendall Houghton

Background Information

Statement of the Problem

Statement of the Hypothesis

Supplies

Procedure

Data

Conclusion

Works Cited

Related Sites

Background Information

Magnets are frequently used in daily life.  For example, magnets are used in manufacturing, entertainment, security, and they play a crucial role in the functioning of computers.  Even the earth itself is a magnet.

A magnet is any object that produces a magnetic field (Wikipedia).  Some magnets, referred to as permanent, hold their magnetism without an external electric current.  A magnet of this nature can be created by exposing a piece of metal containing iron to a number of situations (i.e. repeatedly jarring the metal, heating to high temperature).  Soft magnets, on the other hand, are those that lose their magnetic charge properties over time.  Additionally, paramagnetic objects are those that can become magnetic only when in the presence of an external magnetic field.

A magnetic field is the space surrounding a magnet in which magnetic force is exerted.  The motion of negatively charged electrons in the magnet determines not only the polarity, but also the strength of the magnet (Cold magnet).

Magnets are filled with magnetic lines of force (How magnets Work).  These lines originate at the north pole of the magnet and continue to the south pole.  The north pole is positive.  Magnetic lines of force do not intersect one another.

Magnetism is created by the alignment of small domains within a specific set of metal.  These domains function as all atoms do, thus the temperature affects the movement.  The higher the heat, the greater the energy, and as such the movement of the particles.  In contrast, cold temperature slows the movement (magnetic Field Strength and Low Temperatures).  Slower movement leads to more fixed directions in terms of the domains.

In the 1800’s, Pier4re Curie discovered that there exists a temperature at which objects that were previously permanently magnetic lose this characteristic (Wikipedia).  The temperature at which this demagnetization occurs is called the “Curie point”.  As the temperature of the magnet approaches this point, the alignment of each domain decreases.  As such, the magnetism decreases until the Curie point is reached, at which time the material becomes paramagnetic.

Statement of the Problem

The purpose of this experiment is to determine how extreme temperature affects magnets.  For the given permanent magnet we have obtained, we would like to calculate not only the Curie point, but also the slope of the decrease of magnetism that occurs as said point is approached.

Statement of the Hypothesis

We believe that the colder the magnet, the stronger the magnetic force.  Graphically, our results will resemble an exponential curve, with magnetic force decreasing as temperature increases.  Our independent variable is temperature.  Our dependent variable is magnetism; this will be calculated using the amount of bb pellets that the magnet is able to collect at each measured temperature.

Supplies

• Bowl
• 1,000 BB’s
• Scale
• Magnet
• Oven
• Freezer
• Freezer thermometer

Diagram of Set-Up

Procedure

Cold Process

1. Place BB’s in bowl.
2. Situate scale near bowl.
3. Weigh magnet and record.
4. Place magnet and freezer thermometer in freezer set to lowest temperature possible.
5. Wait approximately 20 minutes for the magnet to reach the temperature of the freezer.
6. Record temperature read by freezer thermometer.
7. Place magnet in bowl filled with BB’s.
8. Remove magnet and attached BB’s and place on scale.
9. Record temperature of magnet and grams attracted.
10. Subtract the weight of the magnet from the weight of the magnet and the BB’s combined.
11. Remove BB’s and place back in bowl.
12. Set freezer to 5-Celsius degrees higher than previous temperature. (Note: freezer accuracy is dubious.  Use temperature read by freezer thermometer)
13. Repeat steps 4-12 until freezer and magnet have reached zero degrees Celsius.

Hot Process

1. Place BB’s in the bowl.
2. Situate scale near bowl.
3. Weigh magnet and record.
4. Place magnet in oven set to highest temperature possible.
5. Wait approximately 20 minutes for the magnet to reach the temperature of the oven.
6. Place magnet in bowl filled with BB’s.
7. Remove magnet and attached BB’s and place on scale.
8. Record temperature of magnet and grams attracted.
9. Subtract the weight of the magnet from the weight of the magnet and the BB’s combined.
10. Remove BB’s and place back in bowl.
11. Allow magnet to rest for 5 minutes undisturbed.
12. Repeat steps 6-11 until magnet reaches room temperature.

Data

Magnet Strength with Colder Temperature

 Temperature (degrees Celsius) Weight Attracted (+/- 2.5 grams) -21.3 275 -19.4 275 -18.1 265 -15.3 270 -13.7 260 -6.7 245 -4.6 220 -1.7 200 0 225

Magnet Strength with Hotter Temperature

 Time After Removal From Oven (minutes) Weight Attracted (+/- 2.5 grams) 0 200 5 200 10 240 20 210 25 230 30 220 35 206 40 204 45 200 50 185

Date File: Text .:. Excel

Conclusion

We were correct in the sense that the colder temperatures did in fact increase the magnet strength.  While the path of the hotter temperatures followed roughly what we had projected, individual date points strayed from our prediction.  We believe this inaccuracy can be attributed to a lack of precision in our procedure.  The process for the hotter magnets involved time instead of temperature and the magnet was not in an isolated environment while cooling.  Additionally, for both of the magnets, the time allowed in the bowl was not regulated as such some trials the magnet may have been allowed to pick up more BB’s than others.

If we were to do the experiment again, we would heat the magnet and the oven to precise temperatures beginning with the cooler temperatures first.  Additionally, we would allow the magnet to reach room temperature from either a cold or hot one before testing it at a different temperature.  We would do multiple trials of each temperature in order to average our results, and thus have more accuracy.  Also, the precision of the scale could be improved upon.  Our measuring device was  in increments of five grams, and therefore our measurements could have a range of +/- 2.5 grams from what we had recorded.

Works Cited

Magnet. 4 Nov. 2008. 4 Nov. 2008

</http:en.wikipedia.org/wiki/magnet#calculating_the_magnetic_force>.

Curie point. 30 Nov. 2008. Wikipedia. 6 Dec. 2008

</http:en.wikipedia.org/wiki/Curie_temperature>.

How Magnets Work! 2006. 4 Nov. 2008

</http://www.howmagnetswork.com/>.

Magnetic Field Strength and Low Temperature. 16 Oct. 2004. Ask a Scientist. 6 Dec. 2008

Cold Magnet. 3 Mar. 1961. Time Magazine. 6 Dec. 2008

</http://www.time.com/time/magazine/article/0,9171,897680-2,00.html>.

Related Sites

http://en.wikipedia.org/wiki/Magnet#calculatin_the_magnetic_force

A description of the general properties of magnets.

http://en.wikipedia.org/wiki/Curie_temperature

A description of the Curie point, the Curie point in ferromagnetic materials, and the Curie temperature in piezoelectric materials.

http://www.howmagnetswork.com/

An explanation of how magnets work: on the earth's magnetic fields, the history of magnets, industrial magnet uses, electromagnetism, and the different types of magnets.

A study on magnet strength and temperature.

www.time.com/time/magazine/article/0,9171,897680-2,00.html

Insight on electromagnetics.