Transcript
Submitted BY: BY: ASHUTOSH KUMAR
CLASS: XII-A
Guided By :Class :XII – A Year :2014- 2015 Roll No :School :JAI HIND PUBLIC SCHOOL
Certified to be the bonafide work is done by Master Ashutosh Kumar of class XII-A in the Physics Lab during the year 2014-2015. Date :-20-01-2015 Submitted for Central Board of Secondary Education. Examination held in Physics lab at Jai Hind Public School EXAMINER
Date :-_________
ACKNOWLEDGEMENT I wish to express my deep gratitude and sincere thanks to the Principal, Mr._____________, Jai Hind Public School for his encouragement and for all the facilities that he provided for this project work. I sincerely appreciate this magnanimity by taking me into his fold for which I shall remain indebted to him. I extend my hearty thanks to Mr. S.L. Sharma, Physics teacher,who guided me to the successful completion of this project. I take this opportunity to express my deep sense of gratitude for her invaluable guidance, constant encouragement , immense motivation , which has sustained my efforts at all the stages of this project work… I can’t forgot to offer my sincere thanks to lab assistant and also to my classmates who helped me to carry out this project work successful and for their valuable advice and support , which I received from them time to time….
1--
Introduction
2-- Objective 3--
Material required
4-- Theory 5-- Procedure 6-- Observation
7--
Conclusion
8-- Bibliography……
OBJECTIVE THE OBJECTIVE OF THIS EXPERIMENT IS TO DETERMINE THE EFFECT OF TEMPERATURE ON THE STRENGTH OF A MAGNET.
HYPOTHESIS
It is believed that the colder the magnet, the stronger the magnetic force. Graphically, the 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 paperclips that the magnet is able to collect at each measured temperature
MATERIAL REQUIRED •
Safety glasses
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3-4 permanent bar magnets
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Tongs for magnet
Ice Water Insulating container
Three strong bowls
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Small pot
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Burner for heating water or oven
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Paper clips(1000)
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 . 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 . 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 . 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.
THEORY A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets. A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include iron, nickel, cobalt, some alloys of rare earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism.
Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do. Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a powerful magnetic field during manufacture, to align their internal microcrystalline structure, making them very hard to demagnetize. To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on coercivity of the respective material. "Hard" materials have high coercivity, whereas "soft" materials have low coercivity. The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces. The local strength of magnetism in a material is measured by its magnetization.
PROCEDURE 1. 2. 3. 4.
Place paperclips in bowl. Situate scale near bowl. Weigh magnet and record. 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 paperclips. 8. Remove magnet and attached paperclips 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 paperclips combined. 11. Remove paperclips 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. .
1. Place paperclips in the bowl. 2. Situate scale near bowl. 3. 4.
Weigh magnet and record. 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 paperclips. 7. Remove magnet and attached paperclips 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 paperclips combined. 10. Remove paperclips and place back in bowl. 11. Allow magnet to rest for 5 minutes undisturbed. 12. Repeat steps 6-11 until magnet reaches room temperature.
OBSERVATION MAGNETS UNDER EXTREME HEAT Time after removal from oven (minutes)
Weight attracted (in grams)
0
200
5
200
10
240
20
210
25
230
30
220
35
206
40
204
45
200
50
185
MAGNETS UNDER EXTREME COLD Temperature (degree celsius)
Weight attracted (in 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
conclusion Magnetic materials should maintain a balance between temperature and magnetic domains (the atoms’ inclination to spin in a certain direction). When exposed to extreme temperatures, however, this balance is destabilized; magnetic properties are then affected. While cold strengthens magnets, heat can result in the loss of magnetic properties. In other words, too much heat can completely ruin a magnet. Excessive heat causes atoms to move more rapidly, disturbing the magnetic domains. As the atoms are sped up, the percentage of magnetic domains spinning in the same direction decreases. This lack of cohesion weakens the magnetic force and eventually demagnetizes it entirely. In contrast, when a magnet is exposed to extreme cold, the atoms slow down so the magnetic domains are aligned and, in turn, strengthened. Ferromagnetism The way in which specific materials form permanent magnets or interact strongly with magnets. Most everyday magnets are a product of ferromagnetism. Paramagnetism A type of magnetism that occurs only in the presence of an external magnetic field. They are attracted to magnetic fields, but they are not magnetized when the external field is removed. That's because the atoms spin in random directions; the spins aren’t aligned, and the total magnetization is zero. Aluminum and oxygen are two examples of materials that are paramagnetic at room temperature. Curie Temperature Named for the French physicist Pierre Curie, the Curie Temperature is the temperature at which no magnetic domain can exist because the atoms are too frantic to maintain aligned spins. At this temperature, the ferromagnetic material becomes paramagnetic. Even if you cool the magnet, once it has become demagnetized, it will not become magnetized again. Different magnetic materials have different Curie Temperatures, but the average is about 600 to 800 degrees Celsius.
BIBLIOGRAPHY www.icbse.com www.sciencebuddies.com www.technopedia.com www.wikipedia.com NCERT
Physics book
www.howmagnetswork.com
