PHYSICS PROJECT - Copy.docx

7/27/2019 PHYSICS PROJECT - Copy.docx

1/21

Effect of temperature on thestrength of a magnet

Physics Project

BY -

Sanay MathurRoll no 1232-A

XII A


2/21

CERTIFICATE

This is to certify that the PHYSICS project has been

successfully completed bySanay Mathurof Class XII A

in partial fulfillment of curriculum ofCENTRAL BOARD

OF SECONDARYEDUCATION (CBSE)leading to the

award of annual examination of the year 2013-2014.

INTERNAL EXAMINER H.O.D PHYSICS


3/21

ACKNOWLEDGEMENT:

F irst and foremost I thank my teacher physics

M r. Suresh Kumar for his remarkable, valuable guidance,

supervision, help and encouragement throughout the project

work.

I would also li ke to thank my parents who helped me a lot in

gather ing information, collecting data and guiding me from

time to time in making thi s project unique.

I would like to acknowledge the assistance provided to me by

the library staff of Army Public School, Bangalore.

Sanay Mathur


4/21

INDEX:

Aim

Introduction Theory

Apparatus

Procedure Observations

Result

Precautions Conclusion

Bibliography


5/21

AIM:To determine howtemperature affects

the strength of amagnet.


6/21

INTRODUCTION:

agnetic fields are produced by electric currents.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 externalmagnetic field.

A magnetic field is the space surrounding a magnet in which

magnetic force is exerted. The motion of negatively charged

M


7/21

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.

Certain materials, called ferromagnetic materials, have

unpaired electrons in their outermost atomic orbits that can

become magnetically aligned over large distances (relative to

the atomic scale). These regions of alignment are

called magnetic domains.

An electric current flowing through a straight wirecreates a magnetic field around the wire.The illustration shows the magnetic

field produced by electric current in

a straight wire. When the thumb of

the right hand is pointing in the

direction of the current, the fingers of

the right hand curl in the direction of

the magnetic field.


8/21

In the 1800s, Pierre Curie discovered that there exists a temperature atwhich objects that were previously permanently magnetic lose thischaracteristic . The temperature at which this demagnetization occurs iscalled the Curie Point. As the temperature of the magnet approachesthis point, the alignment of each domain decreases. As such, themagnetism decreases until the Curie point is reached, at which time thematerial becomes paramagnetic.

THEORY:

A magnetis 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.

Apermanent magnetis 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 alsothe ones that are strongly attracted to a magnet, are called


9/21

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.

Permanent magnets are made from ferromagnetic materials. If a

ferromagnetic material is exposed to a strong magnetic field, the

magnetic domains within the material will retain at least some of the

alignment induced by the external magnetic field.

When the temperature of a material is increased, what is happening

on the atomic scale is an increase in the random motion of the atoms

of which the material is made. Each ferromagnetic material has

a Curie temperature (named after Pierre Curie), above which it can

no longerbe magnetized. For soft iron, the Curie temperature is over

1,300C!

A current flowing through a coil of wire (the coil is also called

a solenoid) creates a stronger magnetic field than the same current

flowing through a straight wire. The magnetic field is strongest at the

center of the coil. Each loop in the coil contributes additional

strength to the magnetic field. The more the loops, the stronger the

field.


10/21

The illustration shows the magnetic field produced by an

electric current in a coil (solenoid). When the fingers of the right

hand curl in the direction of the current flow, the thumb points in

the direction of the magnetic field (i.e. thumb points towardmagnetic North pole of the solenoid).

APPARATUS:

5 permanent magnets


11/21

of equal size and strength.

A pair of tongs.

A thermometer.

Plastic bowl filled with 200 standardsize paper clips.

PROCEDURE:1) The independent variable is the temperature of the magnet - 0C,

25C, 50C, 75C and 100C. The dependent variable is the number of

paper clips picked up by the magnet. This is determined by counting the


12/21

number of paper clips that stick to the magnet. The constants (control

variables) are the size of the magnet and the weight of the paper clips.

2) 5 magnets are kept in the freezer of the refrigerator overnight, in order

for them to stabilize at 0C for use in the experiment.

3) The next day, 200 paper clips are spread in a bowl. The 5 magnets are

removed from the refrigerator and their temperatures are measured using

a thermometer. Wearing gloves, place one of the magnets over the paper

clips in the bowl to pick up as many paper clips as possible. The results

are recorded in the table given below.4) The 5 magnets are placed on a hot plate until a temperature of 25C is

reached. Repeat the 3rd

step using the same 5 magnets and the number of

paper clips picked up is record in the observation table.

5) Repeat steps 3 and 4 by bringing the temperature of the magnets to

50C, 75C and 100C, by placing them on the hot plate. The results arerecorded in the observation table.

OBSERVATIONS:

MAGNET No. of paper clips picked up by the magnets

at different temp.


13/21

0C 25C 50C 75C 100CMAGNET

1

29 25 21 13 8MAGNET

2

34 29 26 16 11MAGNET

3

37 32 28 18 12MAGNET

4

31 27 23 15 9MAGNET

5

28 23 19 12 7


14/21

0

5

10

15

20

25

30

35

40

0C 25C 50C 75C 100C

MAGNET 1

MAGNET 2

MAGNET 3

MAGNET 4

MAGNET 5


15/21

RESULT:

Increasing thetemperature reduces

the strength of the

magnet.


16/21

PRECAUTIONS:

Measure the temperature of the

magnets accurately.

No. of paper clips should be counted

properly.

Magnets should be of equal size.

Paper clips should be of equal size.

Wear gloves so that the body

temperature does not affect the

temperature of the magnets.

Record your observations correctly.


17/21


18/21

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


19/21

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 arent aligned, and the total

magnetization is zero.

Aluminum and oxygen are two examples of materials that are paramagnetic

at room temperature.

Curie TemperatureNamed for the French physicist Pierre Curie,

the Curie Temperatureis 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.


20/21

BIBLIOGRAPHY:

www.icbse.com

www.sciencebuddies.com

www.wikipedia.com

NCERT Physics textbook

www.howmagnetswork.co

m


21/21

PHYSICS PROJECT - Copy.docx

Documents

Transcript of PHYSICS PROJECT - Copy.docx