Hobbies And Interests
Hot and Cold Water
This experimental design for children uses bowls of hot and cold water to alter the temperature of a magnet. Prepare a bowl of ice water and a second bowl of water that is hot, but not too hot to touch. The hot setting on most faucets will be sufficient. Let the child place a bar magnet into one bowl for a few minutes, then use it to pick up a row of nails. Count how many nails the magnet picked up. Repeat after letting the magnet rest in the second bowl and compare the results.
Freezing and Boiling Magnets
Increasing the temperature range will produce a more dramatic variation in magnet strength. Test the weight a magnet can lift at room temperature. Submerge the magnet into boiling water for a few minutes, then test the weight it can lift when it's 100 degrees Celsius. After it cools off, place the magnet in a bowl of ice in the freezer for 10 to 15 minutes, then test how much weight it can lift when it's 0 degrees Celsius. Use nonmagnetic tongs to pick up the hot and cold magnets.
Graphing Loss of Magnetic Strength
Test a magnet's strength at room temperature by seeing how many grams of weight it can lift, either by weighing the ball bearings it can hold or by using it to lift small metal weights. Heat the magnet in increments of 50 degrees Celsius using an oven, a blowtorch or a Bunsen burner. Wear protective gloves and goggles and use nonmagnetic tongs to handle the magnet at high temperatures. Test how much weight the magnet can hold at each temperature increment and graph the results.
Permanent Demagnetization
Each type of magnet has a temperature at which it will become permanently demagnetized, known as the Curie temperature. Neodymium iron boron magnets have the lowest Curie temperature at 310 degrees Celsius. To find the Curie temperature, heat a group of identical magnets in an oven. Use nonmagnetic tongs to remove one magnet as the oven temperature reaches each multiple of 100 degrees Celsius. Mark the maximum temperature each magnet reached and let all of the magnets slowly return to room temperature. Test the magnets to see which ones can still lift metal ball bearings and which have become demagnetized.