PHYSICS SCIENCE UNIT-2 - NIMS Dubai · The CBSE has introduced the CBSE-i curriculum in schools...

ClassX

UNIT -2

Shiksha Kendra, 2, Community Centre, Preet Vihar, Delhi-110 092 India

PHYSICS :

CHEMISTRY :

BIOLOGY :

MAGNETISM

METALS

CONTROL AND COORDINATION

CBSE-i

Science

Shiksha Kendra, 2, Community Centre, Preet Vihar, Delhi-110 092 India

PHYSICS : MAGNETISM

CHEMISTRY : METALS

BIOLOGY : CONTROL AND COORDINATION

CBSE-i

UNIT -2

Science

ClassX

The CBSE-International is grateful for permission to reproduce and/or

translate copyright material used in this publication. The

acknowledgements have been included wherever appropriate and

sources from where the material has been taken duly mentioned. In

case anything has been missed out, the Board will be pleased to rectify

the error at the earliest possible opportunity.

All Rights of these documents are reserved. No part of this publication

may be reproduced, printed or transmitted in any form without the

prior permission of the CBSE-i. This material is meant for the use of

schools who are a part of the CBSE-International only.

PREFACEThe Curriculum initiated by Central Board of Secondary Education -International (CBSE-i) is a progressive step in making the educational content and methodology more sensitive and responsive to the global needs. It signifies the emergence of a fresh thought process in imparting a curriculum which would restore the independence of the learner to pursue the learning process in harmony with the existing personal, social and cultural ethos.

The Central Board of Secondary Education has been providing support to the academic needs of the learners worldwide. It has about 11500 schools affiliated to it and over 158 schools situated in more than 23 countries. The Board has always been conscious of the varying needs of the learners in countries abroad and has been working towards contextualizing certain elements of the learning process to the physical, geographical, social and cultural environment in which they are engaged. The International Curriculum being designed by CBSE-i, has been visualized and developed with these requirements in view.

The nucleus of the entire process of constructing the curricular structure is the learner. The objective of the curriculum is to nurture the independence of the learner, given the fact that every learner is unique. The learner has to understand, appreciate, protect and build on values, beliefs and traditional wisdom, make the necessary modifications, improvisations and additions wherever and whenever necessary.

The recent scientific and technological advances have thrown open the gateways of knowledge at an astonishing pace. The speed and methods of assimilating knowledge have put forth many challenges to the educators, forcing them to rethink their approaches for knowledge processing by their learners. In this context, it has become imperative for them to incorporate those skills which will enable the young learners to become 'life long learners'. The ability to stay current, to upgrade skills with emerging technologies, to understand the nuances involved in change management and the relevant life skills have to be a part of the learning domains of the global learners. The CBSE-i curriculum has taken cognizance of these requirements.

The CBSE-i aims to carry forward the basic strength of the Indian system of education while promoting critical and creative thinking skills, effective communication skills, interpersonal and collaborative skills along with information and media skills. There is an inbuilt flexibility in the curriculum, as it provides a foundation and an extension curriculum, in all subject areas to cater to the different pace of learners.

The CBSE has introduced the CBSE-i curriculum in schools affiliated to CBSE at the international level in 2010 and is now introducing it to other affiliated schools who meet the requirements for introducing this curriculum. The focus of CBSE-i is to ensure that the learner is stress-free and committed to active learning. The learner would be evaluated on a continuous and comprehensive basis consequent to the mutual interactions between the teacher and the learner. There are some non-evaluative components in the curriculum which would be commented upon by the teachers and the school. The objective of this part or the core of the curriculum is to scaffold the learning experiences and to relate tacit knowledge with formal knowledge. This would involve trans-disciplinary linkages that would form the core of the learning process. Perspectives, SEWA (Social Empowerment through Work and Action), Life Skills and Research would be the constituents of this 'Core'. The Core skills are the most significant aspects of a learner's holistic growth and learning curve.

The International Curriculum has been designed keeping in view the foundations of the National Curricular Framework (NCF 2005) NCERT and the experience gathered by the Board over the last seven decades in imparting effective learning to millions of learners, many of whom are now global citizens.

The Board does not interpret this development as an alternative to other curricula existing at the international level, but as an exercise in providing the much needed Indian leadership for global education at the school level. The International Curriculum would evolve on its own, building on learning experiences inside the classroom over a period of time. The Board while addressing the issues of empowerment with the help of the schools' administering this system strongly recommends that practicing teachers become skillful learners on their own and also transfer their learning experiences to their peers through the interactive platforms provided by the Board.

I profusely thank Shri G. Balasubramanian, former Director (Academics), CBSE, Ms. Abha Adams and her team and Dr. Sadhana Parashar, Head (Innovations and Research) CBSE along with other Education Officers involved in the development and implementation of this material.

The CBSE-i website has already started enabling all stakeholders to participate in this initiative through the discussion forums provided on the portal. Any further suggestions are welcome.

Vineet JoshiChairman

ACKNOWLEDGEMENTS

English :

Geography:

Ms. Sarita Manuja

Ms. Renu Anand

Ms. Gayatri Khanna

Ms. P. Rajeshwary

Ms. Neha Sharma

Ms. Sarabjit Kaur

Ms. Ruchika Sachdev

Ms. Deepa Kapoor

Ms. Bharti Dave Ms. Bhagirathi

Ms. Archana Sagar

Ms. Manjari Rattan

Mathematics :

Political Science:

Dr. K.P. Chinda

Mr. J.C. Nijhawan

Ms. Rashmi Kathuria

Ms. Reemu Verma

Ms. Sharmila Bakshi

Ms. Srelekha Mukherjee

Science :

Economics:

Ms. Charu Maini

Ms. S. Anjum

Ms. Meenambika Menon

Ms. Novita Chopra

Ms. Neeta Rastogi

Ms. Pooja Sareen

Ms. Mridula Pant

Mr. Pankaj Bhanwani

Ms. Ambica Gulati

History :

Ms. Jayshree Srivastava

Ms. M. Bose

Ms. A. Venkatachalam

Ms. Smita Bhattacharya

Material Production Groups: Classes IX-X

English :

Ms. Rachna Pandit

Ms. Neha Sharma

Ms. Sonia Jain

Ms. Dipinder Kaur

Ms. Sarita Ahuja

Science :

Dr. Meena Dhami

Mr. Saroj Kumar

Ms. Rashmi Ramsinghaney

Ms. Seema kapoor

Ms. Priyanka Sen

Dr. Kavita Khanna

Ms. Keya Gupta

Mathematics :

Political Science:

Ms. Seema Rawat

Ms. N. Vidya

Ms. Mamta Goyal

Ms. Chhavi Raheja

Ms. Kanu Chopra

Ms. Shilpi Anand

Geography:

History :

Ms. Suparna Sharma

Ms. Leela Grewal

Ms. Leeza Dutta

Ms. Kalpana Pant

Material Production Groups: Classes VI-VIII

Advisory Conceptual Framework

Ideators

Shri Vineet Joshi, Chairman, CBSE Shri G. Balasubramanian, Former Director (Acad), CBSE

Shri Shashi Bhushan, Director(Academic), CBSE Ms. Abha Adams, Consultant, Step-by-Step School, Noida

Dr. Sadhana Parashar, Head (I & R),CBSE

Ms. Aditi Misra Ms. Anuradha Sen Ms. Jaishree Srivastava Dr. Rajesh Hassija

Ms. Amita Mishra Ms. Archana Sagar Dr. Kamla Menon Ms. Rupa Chakravarty

Ms. Anita Sharma Ms. Geeta Varshney Dr. Meena Dhami Ms. Sarita Manuja

Ms. Anita Makkar Ms. Guneet Ohri Ms. Neelima Sharma Ms. Seema Rawat

Dr. Anju Srivastava Dr. Indu Khetrapal Dr. N. K. Sehgal Dr. Uma Chaudhry

Coordinators:

Dr. Sadhana Parashar, Ms. Sugandh Sharma, Dr. Srijata Das, Dr. Rashmi Sethi, Head (I and R) E O (Com) E O (Maths) E O (Science)

Shri R. P. Sharma, Consultant Ms. Ritu Narang, RO (Innovation) Ms. Sindhu Saxena, R O (Tech) Shri Al Hilal Ahmed, AEO

Ms. Seema Lakra, S O Ms. Preeti Hans, Proof Reader

Material Production Group: Classes I-V

Dr. Indu Khetarpal Ms. Rupa Chakravarty Ms. Anita Makkar Ms. Nandita Mathur

Ms. Vandana Kumar Ms. Anuradha Mathur Ms. Kalpana Mattoo Ms. Seema Chowdhary

Ms. Anju Chauhan Ms. Savinder Kaur Rooprai Ms. Monika Thakur Ms. Ruba Chakarvarty

Ms. Deepti Verma Ms. Seema Choudhary Mr. Bijo Thomas Ms. Mahua Bhattacharya

Ms. Ritu Batra Ms. Kalyani Voleti

Content

PHYSICS

1. SYLLABUS COVERAGE - 3

Core

2. SCOPE DUCUMENT - Physics 4

Learning Outcomes

Cross Curricular links

3. Teacher Student Activities - Physics 5

4. LESSON TEMPLATES - Physics 6

5. Rubrics Of Assessment For Learning - Physics 34

Physics

2

2

2

CHEMISTRY5. SYLLABUS COVERAGE - 37

Core And Extension

6. SCOPE DUCUMENT - Chemistry 38

Learning Outcomes


7. LESSON TEMPLATES - Chemistry 40

8. Rubrics Of Assessment For Learning - Chemistry 136

Chemistry

2

2

2

BIOLOGY9. SYLLABUS COVERAGE - 139

Core And Extension

10. SCOPE DUCUMENT - Biology 140

Learning Outcomes


11. LESSON TEMPLATES - Biology 144

Biology

2

2

2

PhysicsUnit 2

MAGNETISM

SCIENCE UNIT-2 PHYSICS3

S

Y

L

L

A

B

U

S

2

2

2

2

2

2

2

2

2

Magnets and Magnetic Materials

Properties of magnet

Difference between permanent magnets and electromagnets

Magnetic field around a current carrying conductor

Maxwell's right hand grip rule

Uses of magnets and electromagnets

Force on a current carrying conductor placed in a magnetic field

Fleming's left hand rule

Function and working of Electric motor

Core

Syllabus Coverage

Unit 2 - MAGNETISM

Physics

SCIENCE UNIT-2PHYSICS

Learning outcomes

Cross curricular links

At the end of this unit, students should be able to

Describe and identify magnets and magnetic materials.

Describe properties of magnet.

Differentiate between permanent magnet and an electromagnet.

Describe magnetic field around a current carrying wire and a solenoid.

Explain uses of magnets and electromagnets.

Understand and describe that a current carrying conductor when placed inside a magnetic field experiences a force.

Describe factors that affect the force on a current carrying conductor placed in a magnetic field.

State and explain Fleming's Left Hand Rule.

Describe the construction and working of an electric motor.

History - History of magnets and magnetism.

Geography - Uses of compass needle and magnets in finding directions.

Biology - Uses of magnetism in the field of medicine.

SCOPE DOCUMENT

4

SCIENCE UNIT-2 PHYSICS

Teacher's Activity Student's ActivitySteps to be

followed

SYLLABUS COVERAGE - Physics Page no- Core and Extension1.

SCOPE DOCUMENT- Physics Page no

Learning Objectives

Cross Curricular Links

Suggested Activities

C

C

C

2.

LESSON TEMPLATE- Physics Page no 3.

S t u d e n t - T e a c h e r S u p p o r t Material-Physics

Page number 4.

Rubrics of Assessment- Physics Page no 5.

S Y L L A B U S C O V E R A G E - Chemistry

Page no

Core and Extension

6.

SCOPE DOCUMENT- Chemistry Page no

Learning Objectives



C

C

C

7.

LESSON TEMPLATE- Chemistry Page no-8.

S t u d e n t - T e a c h e r S u p p o r t Material- Chemistry

Page no -9.

Rubrics of Assessment-Chemistry Page no -10.

SYLLABUS COVERAGE- Biology Page no -

Core and Extension

11.

SCOPE DOCUMENT- Biology Page no-

Learning Objectives



C

C

C

12.

LESSON TEMPLATE- Biology Page no -13.

S t u d e n t - T e a c h e r S u p p o r t Page no -14.

Material- Biology

Rubrics of Assessment-Biology

Page no -15.

5


Teacher's Activity Student's ActivitySteps to be

followed

Teacher may start the class by

discussing the devices which rely

on magnets for their working.

Students will understand the

role of magnets for the

working of some devices .

Pre content

Warming Up

Activity

T e a c h e r m a y e x p l a i n t h e

properties of magnetic materials

with the help of activity 1.

Students will try to answer

t h e q u e s t i o n s a n d

d i f f e r e n t i a t e b e t w e e n

magnetic and non magnetic

materials.

Content

Development

Student Teacher

Material

1. Magnetic

Material

Teacher may explain the reason for

the property of attraction of

magnets using Domain Theory.

He/She may explain the different

types of magnets with the help of

activities and questions.

Activity 2 and 2.1


working and types of

magnets through activities.

2. Magnetic

Domain

2.1 Types of

Magnet

LESSON TEMPLATE

Teacher may demonstrate the

properties of a magnet With the

help of Experiments 3.1,3.2,3.3 and

3.4. He/She may also explain

earth's magnetism.


properties of a magnet like, it

points towards north south

direction etc. with the help of

experiments.They will also

gain the knowledge about

earth's magnetism.

3. Properties of a

magnet

Teacher may explain the term

electromagnetism with the help of

a n a c t i v i t y . T e a c h e r m a y

demonstrate the making of an

electromagnet and determining

the direction of the field around a

current carrying conductor using

the Right Hand Grip rule.


term electromagnetism.

They will learn how to make

an electromagnet and find

the direction of magnetic

field around a current

carrying conductor.

4.

Electromagnetism

4.1 Electromagnet

4.2 Maxwell's

RIGHT Hand

Grip Rule

6


Activity 4 and 4.1

http://www.metacafe.com/watc

h/1097288/build_an_electromag

net/

Students will gain the

knowledge about the various

uses of magnets

5. Uses of

Magnets

Teacher may explain the uses of

magnets using daily life examples.

Read more: Everyday Uses of

Magnets | eHow.com

http://www.ehow.com/facts_5314

850_everyday-uses-

magnets.html#ixzz1GC0tXgZr

Students will understand

the concept through

demonstrations.

6. Force

Experienced

by a current

carrying

conductor

placed in a

magnetic field.

6.1 Flemings Left

Hand Rule

Teacher may explain that a current

carrying conductor experiences a

force when kept in a magnetic field

with the help of a Java Applet and

an activity (activity 6). Teacher

may also explain the use of

Fleming's Left Hand Rule.

http://www.youtube.com/watch?

v=14SmN_7EcGY


working and usage of electric

motor.

7. Construction

and Working of

an Electric Motor

Teacher may use the PowerPoint

Presentation provided herewith to

explain the construction and

working of an electric motor.

Students will attempt the

revision worksheets given to

them.

8. Revision

8.1 Worksheet 1

8.2 Worksheet 2

T e a c h e r m a y a s s e s s t h e

understanding of the unit by

using the given worksheets

Students will work on the

given projects.

9. Projects Teacher may ask the students to

work on the given projects

individually or in groups

7


TEACHER'S NOTESFLOW CHART FOR MAGNETISM

Warm Up Activity

Activity on Properties of magnetic material Questions for discussion

Activities on Magnetic Domain Questions for Discussion

Hands on Experiments on properties Questions for Discussion

Of Magnets

Demonstration on Electromagnetism Questions for Discussion

Right Hand Grip rule Model Making

Electromagnet

Explanation of uses of magnet Suggestive Links

With the help of daily life Examples

Demonstration of Force on a current

Carrying conductor using Java Applet Fleming's left hand rule

Questions

Demo of working of an electric motor

Using the given PPT Project

Summative Assessment Sheets

8


WARM UP ACTIVITY;

THE MYSTERY OF MAGNETISM

Learning objective -

Identify a number of common items that rely on magnetism to work.

Each time we turn on a light, listen to our stereo, fly in an airplane, or watch TV, we are depending on the principles of magnetism to work for us. Take a look at the pictures below. Identify what these pictures have to do with magnetism?

Can you imagine how your life might be affected without these? What do you think magnetism has to do with each of these things? Think about these questions as you explore these materials on magnetism.

Hydroelectric Dam

Video Cassette Tape

Airplane Navigational Panel

Fan

Magnetic Particle Inspection Unit-

9


ACTIVITY 1 : MAGNETIC MATERIAL

Questions for discussion:

Learning Objective:

Material required:

Students will be able to identify what materials are magnetic and explain why we think they are magnetic.

Magnet, pencil, ball, keys, glass prism, scissors etc.

Teacher will slide the magnet over the collected material and students will note down the observations and answer the following questions.

What conclusions can you draw about the items given in the activity?

What is a magnet?

How do you think something becomes a magnet?

What do you think is different about the items that get attracted to a magnet and items that do not?

What do you think about the origin of magnetism?

How small can a magnet be?

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Just like when the Greeks of the old times discovered the first naturally occurring magnetic stones, or natural magnets, you have been observing a property of matter called magnetism. Magnetism is observing the effects of the force of attraction or repulsion in and around a magnet. Magnetism is relevant for all materials but it is usually at such low levels that it is not easily appreciated. Certain materials such as magnetite, iron, steel, nickel, cobalt and alloys of rare earth elements, exhibit magnetism at levels that are easily detectable.

We usually think of a magnet as any piece of material that has the property of attracting iron (or steel). Magnetite, also known as lodestone, is a naturally occurring rock that is a magnet. This natural magnet was first discovered in a region known as magnesia and was named after the area in which it was discovered. Magnetism may be naturally present in a material or the material may be artificially magnetized by various methods. Magnets may be permanent or temporary. After being magnetized, a permanent magnet will retain the properties of magnetism indefinitely. A temporary magnet is a magnet made of soft iron that is usually easy to magnetize; however, temporary magnets lose most of their magnetic properties when the magnetizing cause is discontinued. Permanent magnets are usually more difficult to magnetize, but they remain magnetized. Materials which can be easily magnetized are called ferromagnetic materials. We will talk more about making a magnet later on.

A magnet can be cut into smaller and smaller pieces indefinitely. However, we find that even the smallest piece still acts as a small magnet. Thus, the cause of magnetism must be from a property of the smallest particles of the material, the atoms. So what is it about the atoms of magnets, or objects that can be magnetized (ferromagnetic materials), that is different from the atoms of other material? For example, why is it that copper keys or aluminum cans cannot be magnetized?

11


ACTIVITY 2 : MAGNETIC DOMAIN

Learning Objective:

Student will be able to define a magnetic domain.

Explain one way of magnetizing an object.

Material required; Magnet, a piece of metal {paper clip}

Teacher rubs the piece of given metal with a strong magnet repetitively in one sense only and demonstrates the magnetic properties developed in the metal piece. Teacher can use following diagrams to explain magnetic domains.

Step 1

Step 2

A magnetic domain is region in which the magnetic fields of atoms are grouped together and aligned. In the experiment above, the magnetic domains are indicated by the arrows in the metal material. You can think of magnetic domains as miniature magnets within a material. In an unmagnetized object, like the initial piece of metal in our experiment, all the magnetic domains are pointing in different directions. But, when the metal became magnetized, which is what happens when it is rubbed with a strong magnet, all like magnetic poles get lined up and point in the same direction. The metal became a magnet. It would quickly become unmagnetized when its magnetic domains returned to a random order. The metal in our experiment is a soft ferromagnetic material, which means that it is easily magnetized but may not retain its

magnetism very long.

Click and drag the magnet across the metallic strip.The arrows represent the alignment of the atoms in the metallic strip.

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What happened to the piece of metal when you rubbed a strong magnet across it the first time? The second time?

What do the arrows in the material represent?

Why do they become lined up when the magnet is brought in contact with the metal?

If you wanted to turn a paper clip into a magnet, how do you think you could do it?

We can turn a paper clip into a magnet by rubbing a strong magnet several times over the surface of the paper clip. The more you drag the magnet over the paper clip, the stronger the paper clip will become magnetized. The same thing happened with the metal in the experiment. When we rubbed the magnet over the surface of the metal, some of the magnetic domains aligned and the metal became partially magnetized. When we rubbed the magnet over the metal a second time, more of the magnetic domains became aligned and the metal became a stronger magnet.

In ferromagnetic materials, the magnetic moments of a relatively large number of atoms are aligned parallel to each other to create areas of strong magnetization within the material. These areas, which are approximately a millimeter in size, contain billions of aligned atoms and are called magnetic domains. Magnetic domains are always present in ferromagnetic materials due to the way the atoms bond to form the material. However, when a ferromagnetic material is in the unmagnetized condition, the magnetic domains are randomly oriented so that the magnetic field strength in the piece of material is zero.

In the unmagnetized condition, the material will be attracted to a magnet but will not act as a magnet. That is to say, two unmagnetized pieces of ferromagnetic material will not be attracted to each other. When a ferromagnetic material is magnetized, the magnetic domains align parallel to each other to produce a large net field strength in the material and the material becomes magnetic.

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ACTIVITY 2.1 : TYPES OF MAGNET


Student will be able to do the following:

Explain the differences between a permanent magnet and a temporary magnet.

Explain why some materials have magnetic properties only when a permanent magnet is near them.

Strong magnet, number of paper clips.

Teacher will demonstrate how a magnet attracts a paper clip, which further attracts more clips. Students will answer the following questions.

What is happening in this experiment?

What conclusions can you draw about magnets and magnetism from this experiment?

We have noted, in previous discussions that magnets can be permanent or temporary. A permanent magnet is more difficult to magnetize but will retain the properties of magnetism indefinitely. A temporary magnet is generally made of soft iron and will remain magnetized only as long as the magnetizing cause is present. From previous experiments you saw how the difference in magnetized and unmagnetized material depends on the motion and arrangement of the material's molecules. Bringing a ferromagnetic object, like a nail, into the magnetic field of a strong magnet, can cause the molecules of the iron material to line up and the nail to become a temporary magnet. As long as it is in the magnetic field of the bar magnet, the nail acts like a magnet and picks up other ferromagnetic materials. In this case it is the paper clip. Then, the paper clip becomes a magnet and can pick up another paper clip, and so forth.

Learning Objective:

Material required:

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ACTIVITY 3 : PROPERTIES OF MAGNETS

Student will be able to

Explain what a compass is and how it is affected by a magnet.

Understand how a compass helps us to navigate on the earth.

Explain how two ends of the magnet behave.

Two Ordinary bar magnets, regular compass

Experiment 3.1 : Students will tie a bar magnet with a thread, tied at the centre and suspend it freely with the help of a support.

Experiment 3.2 : Students will move the given two bar magnets close to each other, keeping the North pole of one pointing towards South pole of the other.

Experiment 3.3 : Students will move the given two bar magnets close to each other, keeping the South pole of one pointing towards South pole of the other.

Experiment 3.4 : Teacher will tell the students to circle the compass needle around the bar magnet and record / mark the direction of the compass needle at all points. Alternatively students can be told to place a bar magnet on a cardboard, sprinkle iron fillings around it and tap the board lightly.

Learning Objective:

Material required :

15



What happened to the blue pole of the compass arrow when it was brought close to the north pole of the magnet?

What happened to the blue pole of the compass arrow when it was brought close to the south pole of the magnet?

What is a compass and what direction does it always point?

What would you expect to happen if a magnet is suspended by a string and allowed to hang freely?

From your observations, what can you conclude about the earth's magnetic properties?

What we have been observing is the behavior of the north and south poles of a magnet. One end of any bar magnet will always want to point north if it is freely suspended. This is called the north-seeking pole of the magnet, or simply the north pole. The opposite end is called the south pole. The needle of a compass is itself a magnet, and thus the north pole of the magnet always points north, except when it is near a strong magnet. In Experiment 1, when we bring the compass near a strong bar magnet, the needle of the compass points in the direction of the south pole of the bar magnet. When we take the compass away from the bar magnet, it again points north. So, we can conclude that the north end of a compass is attracted to the south end of a magnet.

This can be a little confusing since it would seem that what we call the North Pole of the Earth is actually its magnetically south pole. Remember that a compass is a magnet and the north pole of a magnet is attracted to the south pole of a magnet. This situation is also seen in Experiment 1 & 2. In Experiment 2, when we move the north pole of a magnet toward the south pole of the other magnet, the two magnets attract. However, in Experiment 3, when we move the south pole of a magnet toward the south pole of another magnet, the two magnets repel each other and we cannot move them together. The rule for magnetic poles is that like poles repel each other and unlike poles attract each other.

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Since the north seeking pole of a compass always wants to point north, then the compass could be useful in helping us navigate. With a compass we can always tell which direction is north and if we know north, then we know all of the other directions. A compass and a map are essential tools when hiking in the woods. Since the north seeking pole of the compass needle is always attracted to the north, then the earth must be like a huge magnet with a magnetic pole at each end. This is exactly the case but magnetic north is slightly different from the north defined for the axis of rotation of the earth. Scientists believe that the movement of the Earth's liquid iron core and other things are responsible for the magnetic field around the earth.

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ACTIVITY 4 : ELECTRO MAGNETISM

After reading this section, students will be able to do the following:

Describe how a magnetic field is created.

Explain how the electromagnet and the solenoid work together.

Material Required; simple compass and piece of wire connected to a battery & on-off switch.

Teacher will demonstrate that initially the compass will point North but when current passes through the wire kept nearby and perpendicular to the plane containing the compass, the needle deflects. When the direction of flow of current is reversed needle deflects in opposite direction.

Questions for discussion;

What happens to the compass needle as the compass moves around the wire carrying electrical current?

Why do you think this happens?

We can conclude from this experiment that an electric current causes a magnetic field around it just like a magnet causes a magnetic field. When you moved the compass near a bar magnet, the needle pointed toward the magnet's magnetic field and not toward the north. When you put the compass near the electrical wire with current flowing through it, the compass did not point north; instead, the compass needle pointed in the direction of the current's magnetic field.

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Historical Background:

In 1820, a Danish scientist named Hans Oersted discovered that a magnetic compass could be deflected from its resting position if a wire, carrying electric current, was placed near the compass. This deflection of the compass only occurred when current was flowing in the wire. When current was stopped, the compass returned to its resting position.

This graphic seems to indicate that any wire in which an electric current is flowing is surrounded by an invisible force field called a magnetic field. For this reason, any time we deal with current flowing in a circuit, we must also consider the effects of this magnetic field. We have all probably had experiences with magnets at one time or another. Magnets can easily attract certain types of material like iron but almost nothing else.

The term electromagnetism is defined as the production of a magnetic field by current flowing in a conductor. We will need to understand electromagnetism in greater detail to understand how it can be used to do work.

Coiling a current-carrying conductor around a core material that can be easily magnetized, such as iron, can form an electromagnet. The magnetic field will be concentrated in the core. This arrangement is put to use in a device called a solenoid. The more turns we wrap on this core, the stronger the electromagnet and the stronger the magnetic lines of force become.

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ACTIVITY 4.1 : ELECTRO MAGNET

Teacher's instructions :

Learning Objectives :

Material required :

http://www.metacafe.com/watch/1097288/build_an_electromagnet/

Students will be able to understand that

Wrapping the wire around a piece of iron creates a electromagnet.

One iron nail fifteen centimeters (6 in) long, Three meters (10 ft) of

22 gauge insulated, stranded copper wire, One or more D-cell batteries and a pair of wire strippers

Use a pair of wire strippers to remove a few centimeters of

insulation from each end of the wire. Neatly wrap the wire around the nail. The more wire you wrap around the nail, the stronger your electromagnet will be. Make certain that you leave enough of the wire unwound so that you can attach the battery.

When you wrap the wire around the nail, make certain that you wrap the wire all in one direction. You need to do this because the direction of a magnet field depends on the direction of the electric current creating it. If you wrap some of the wire around the nail in one direction and some of the wire in the other direction, the magnetic fields from the different sections fight each other and cancel out, reducing the strength of your magnet.

Attach one end of the wire to the positive terminal of the battery and the other end of the wire to the negative terminal of the battery. If all has gone well, your electromagnet is now working!

Try experimenting with more number of turns of wire, increasing the current or using different cores of varied thickness.

Caution! Too much current can be dangerous! As electricity passes through a wire, some energy is lost as heat. The more current that flows through a wire, the more heat is generated. If you double the current passing through a wire, the heat generated will increase 4 times!

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An electromagnet, which behaves just like a regular permanent bar magnet when the current is flowing. Notice that all of the lines of force pass through the center of the core material, regardless of how they extend outside the coil of wire. The direction of magnetic polarity is determined by the direction of current flowing in the coil of wire. The direction that the wire is coiled around the core also determines the direction of magnetic polarity. This is important to know if we want to use the electromagnet to apply a force to another material.

A magnetic field is generated whatever an electric current flows through a conductor.

The magnetic field around the conductor flows in closed loops.

Wrapping the wire into a coil creates an electromagnet.

Wrapping the wire around a piece of iron creates a solenoid.

Remember that electrons always have a negative electrostatic field surrounding them. When energy, from a power source, such as a battery, is applied to a circuit, making the electrons flow through a conductor, a new type of field is developed around the wire. This is called an magnetic field.

We can see in the diagram below, the magnetic field that surrounds a current-carrying conductor is made up of concentric lines of force. The strength of these circular lines of force gets progressively smaller the further away from the conductor we get. Also, if a stronger current is made to flow through the conductor, the magnetic lines of force become stronger. As a matter of fact, we can say that the strength of the magnetic field is directly proportional to the current that flows through the conductor.

Review

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The term magnetic field intensity is used to describe the strength of the magnetic field. From now on we will use this new term to describe this field that is developed around a conductor that is carrying electrical current.

We have observed that this magnetic force field is a result of current flowing in a conductor. We have also shown that the pattern of this field is circular in shape. What we do not yet know is what direction the circular field is in.

A number of different rules have been developed to help determine the direction of the magnetic field relative to the current. "The right-hand rule" is the simplest to remember and can be used to determine the direction of the magnetic field around a current carrying conductor. With this rule, when the thumb of the right-hand is pointing in the direction of current flow, the sense of curling, of the fingers will be along the direction of the magnetic field.

Field intensity is a term used to describe the strength of the magnetic field.

Field intensity is determined by the amount of electrical current flowing in the wire.

The right-hand rule can be used to describe the direction of the magnetic field.

4.2 Maxwell's Right Hand Grip Rule

Review

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ACTIVITY 5 : USES OF MAGNETS

Magnets are also used to design electric motors and generators. Without these electric motors and generators we would not have telephones, electric lights, electric heaters, television, or computers.

1. Sometimes magnets are used to sort magnetic and non-magnetic materials.

Food manufactures use magnets to keep small metal filings from getting into food.

Candy and coke venders use magnets to separate coins from slugs that are put into their machines.

2. At home, we use magnets to hold things up or to pick up small things: Some examples of this are:

sewing pins

electric can openers

Magnets can hold things to the refrigerator.

1. Sometimes magnets are used to sort magnetic and non-magnetic materials.

Food manufactures use magnets to keep small metal filings from getting into food.

Candy and coke venders use magnets to separate coins from slugs that are put into their machines.

2. At home, we use magnets to hold things up or to pick up small things: Some examples of this are:

sewing pins

electric can openers

Magnets can hold things to the refrigerator.

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3. Magnets are also used in compasses to show attraction and repulsion. Magnetized compasses are used to detect underground metal pipes. A magnetic compass helps us in finding direction also.

4. Magnets are a simple, reliable way to latch doors on refrigerators and cabinets.

5. From tiny ear buds to stadium PA systems, every speaker has a magnet in it. The stronger the magnet, the better the sound quality.

6. DC motors have a set of permanent magnets and electromagnets inside. When connected to a battery, the electromagnets repel the permanent magnets and make the motor spin.

7. Credit cards have a strip of magnetic material on their back side. Account data are recorded on it in a special, machine-readable format.

8. According to Chinese inscriptions in 2000 BC, 'lodestones' were used in acupuncture treatments. Hindu sacred writings also refer to the use of 'lodestones' in the treatments of disorders. Likewise, the Greeks and the Egyptians also utilized them to cure various diseases. Ancient physicians described how magnets had the ability to cure melancholy, arthritis, and baldness.

Nowadays, tectonic magnets are used by many sportsmen to reduce or relieve pain. They are placed on the innersoles of shoes, and are designed in such a manner that they would make contact with the acupressure points present on the soles of the feet. This technique is proven to be helpful for the feet, especially on long walks. Magnetic mattress pads also provide relaxation to the body, and are very helpful for insomniacs. Magnetic beds are used to provide easiness to the nervous system, which may make a person emotionally and physically loosened up. Magnets are also used in X-Rays, and Magnetic Resonance Imaging (MRI) technology, which enables one to know how body tissues respond to the magnetic fields.

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9. Magnets are a very important part of a televisions. The Cathode Ray Tubes (CRT) consist of an electron gun in their neck, which shoots a stream of electrons on the screen. Generally, the electrons are released in a straight line, and impact the center point of the screen. Electromagnets which are present in the tube's neck turn away the electrons towards the top, bottom, right, or left side of the tube. This process makes the inside coating of the screen to glow, which enables images and videos to be shown on the television.

10. Magnets also play an important role in computer disks which are coated with iron material that store small magnetic fields in a specific format. Moreover, magnets are incorporated in computer monitors who work in the same manner as a television. Video tapes consist of same components along with iron compounds, which enable the magnetic fields to be stored in a particular fashion on the tape.

11. Household accessories and items like loudspeakers, home theaters, headphones, telephone receivers, etc., also include magnets in their mechanism.

12. Powerful magnets such as conveyor magnets are used in industries to carry out their manufacturing operations. During the production process, goods are transferred from one place or process to the other, using conveyor belt systems. This is usually done in the case of plastic, wood, or food processing. The conveyor magnets are responsible for removing all metal waste materials from the goods on the conveyor belt, leaving only the pure needed components for further processing. The magnet prevents the metal waste from being included in the later processes such as grinding. In the same manner, magnets are installed in large machinery which makes their respective operations easy and quick.

13. Some items that use electromagnets are: Maglev trains, car crushers, scrap metal sorters, telephones, computers, doorbells, tape recorders etc.

Maglev trains use super conducting magnets in the track and on the underside of the train to "float" above the track. Maglev trains use magnetic repulsion. Maglev trains can travel very fast, up to 480 km/h (300 mph). These Maglev trains are being used in Japan. This train line opened in April 1997. In April of 1999 this train was clocked at an incredible 343 miles an hour! The United States government has set aside 1 billion dollars to build a Maglev train.

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An electromagnet is being used to sort metals in a scrap yard.

Electricity is used to make a temporary magnet, called an electromagnet to run a car crusher. As long as the electric current is on, the iron crane is a magnet and can pick up ferromagnetic objects. When the electricity is turned off, the magnetizing cause is no longer present, so the object is not attracted to the iron crane and it falls into the crusher.

Magnets are important components in most of the things that we use daily. As technology progresses, there would be more and more functions and uses of magnets coming up in various systems and machinery.

Read more: Everyday Uses of Magnets | eHow.com

http://www.ehow.com/facts_5314850_everyday-uses

magnets.html#ixzz1GC0tXgZr

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6. Force on a current- carrying conductor in a magnetic field

Learning Objectives:

Oersted's experiment shows that a current carrying wire exerts a force on a magnetic needle and deflects it from its usual north-south position. The reverse must also be true, which was proved by the French scientist Andre Marie Ampere, who suggested that a magnet must also exert an equal and opposite force on the current carrying conductor. The above mentioned concept can be best understood by way of a demonstration as explained below.

http://www.youtube.com/watch?v=14SmN_7EcGY

1. A current carrying conductor experiences a force when placed in a magnetic field.

2. The direction of force is reversed when the direction of current in the conductor is reversed.

A small aluminum rod AB (5 cm in length) is connected to the wires and suspended horizontally as shown in the fig.

A strong horse-shoe magnet is placed in such a way that the magnetic field is directly upwards and is placed vertically.

The rod AB is connected in series to a battery, a key and a rheostat. Current is switched on and the rod AB gets displaced.

ACTIVITY : 6

Demonstration activity to be done by the Teacher

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Teacher can repeat the experiment by changing the direction of flow of current and also by reversing the direction of magnetic field. Students can be told to note and explain why the rod gets displaced in reverse direction in each case.

Fleming's left hand rule helps us to predict the movement of a current carrying conductor placed in a magnetic field.

According to this rule, extend the thumb, forefinger, and the middle finger of the left hand in such a way that all the three are mutually perpendicular to each another. If the forefinger points in the direction of the magnetic field and the middle finger in the direction of the current, then, the thumb points in the direction of the force exerted on the conductor.

Devices that use current carrying conductors and magnetic fields include electric motors, generators, loudspeakers and microphones.

An electric motor is a device which converts electrical energy into mechanical energy. A common motor works on direct current. So, it is also called DC motor.

When a rectangular coil carrying current is placed in a magnetic field, a torque acts on the coil which rotates it continuously.

When the coil rotates, the shaft attached to it also rotates and thus it is able to do mechanical work.

ACTIVITY 6.1. FLEMING'S LEFT HAND RULE

ACTIVITY 7 : ELECTRIC MOTOR

Principle

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Construction and Working - Parts of a DC Motor

Armature

Commutator

Brushes

Working of a DC Motor

A D.C. motor consists of a rectangular coil made of insulated copper wire wound on a soft iron core. This coil wound on the soft iron core forms the armature. The coil is mounted on an axle and is placed between the cylindrical concave poles of a magnet.

A commutator is used to reverse the direction of flow of current. Commutator is a copper ring split into two parts C1 and C2. The split rings are insulated form each other and mounted on the axle of the motor. The two ends of the coil are soldered to these rings. They rotate along with the coil. Commutator rings are connected to a battery. The wires from the battery are not connected to the rings but to the brushes which are in contact with the rings.

Two small strips of carbon, known as brushes press slightly against the two split rings, and the split rings rotate between the brushes.

The carbon brushes are connected to a D.C. source.

When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn towards the right, causing rotation.

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When the coil turns through 90°, the brushes lose contact with the commutator and the current stops flowing through the coil.

However the coil keeps turning because of its own momentum.

Now when the coil turns through 180°, the sides get interchanged. As a result the commutator ring C is now in contact with brush B and commutator ring C is in 1 2 2

contact with brush B . Therefore, the current continues to flow in the same direction.1

Refer to ppt 'Magnetic Effects of Current’

Increasing the number of turns in the coil

Increasing the strength of the current

Increasing the area of cross-section of the coil

Increasing the strength of the radial magnetic field

Q.1 Name two important properties of a magnet.

Q.2 What is the direction of magnetic field lines inside a magnet?

Q.3 Draw magnetic field lines to depict uniform magnet field.

Q.4 What type of magnetic field lines represent uniform magnetic field?

Q.5 What is the form of magnetic field lines due to a straight current carrying conductor?

Q.6 Name the rule used to find the direction of magnetic field due to a straight current carrying conductor.

Q.7 How do we determine the direction fo magnetic field at a point due to a given source.

The Efficiency of the DC Motor Increases by:

REVISION

8.1. WORKSHEET 1

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Q.8 Name the unit of magnetic field.

Q.9 What is a solenoid?

Q.10 For what purpose do we apply clock rule (end rule)?

Q.11 What is the effect of inserting a soft iron core inside a current carrying solenoid?

Q.12 What type of core is used to make an electromagnet?

Q.13 What are permanent magnets made of?

Q.14 Why is soft iron not used for making a permanent magnet?

1. If one doubles the number of coils and doubles the voltage applied across a coil, what would be the increase in magnetic strength?

(a) It would remain the same, since 2 / 2 = 1

(b) It would be 4 times as strong, since 2 x 2 = 4

© You can't increase magnetism by increasing the voltage

2. Why should the wire around the iron core be insulated?

(a) So that you don't create a short circuit

(b) To keep the iron from getting too warm

(c) To insulate the magnetism

3. Why does an iron core increase the magnetic field of a coil of wire?

(a) The iron atoms line up to add to the magnetic field

(b) Iron attracts things, including magnetic fields

(c) The iron core actually decreases the field, allowing it to be turned off

8.2 WORKSHEET 2

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4. Draw the pattern of the magnetic field produced by electric current flowing through a straight wire and through a wire coil:

Explain your answer using either the right-hand rule (conventional flow) or the left-hand rule (electron flow).

5. If an electric current is passed through this wire loop, in which position will it try to orient itself?

If this experiment is carried out, it may be found that the torque generated is quite small without resorting to high currents and/or strong magnetic fields. Devise a way to modify this apparatus so as to generate stronger torques using modest current levels and ordinary magnets.

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9. PROJECTS

Visit www.novitachopra.blogspot.com to further understand the concepts of Lenz Law and ac generator through Java applets and complete the assignment titled "Magnetic Effects of Current".

Visit www.physicsmantra.ning.com to learn making of simplest electric dc motor and generator through videos and submit a working model of dc motor under your physics project.

Make ppt/brochure/handouts to illustrate the daily life impact of magnetic effects of current and use of electric motors and generators in domestic affairs

Study the electrical circuit of your house {under parental supervision}, collect data, draw circuit diagrams and make a presentation on precautions and safety measures to be taken in domestic electrical circuits and appliances to avoid overloading and shock.

Research work - visit a hospital / pathology lab or take a virtual tour on the net and talk to experts to study Magnetic Resonance Imaging {MRI}. Investigate further how magnetism can be used in medicine

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RUBRICS OF ASSESSMENT FOR LEARNING

Unit 2 - MAGNETISM

Parameter

Learner is able to

Beginning

(1)

Approaching

(2)

Meeting

(3)

Exceeding

(4)

Describe and identify magnets and magnetic materials.

D e s c r i b e p r o p e r t i e s o f magnet.

D i f f e r e n t i a t e b e t w e e n permanent magnet and electromagnet.

Describe magnetic field around a current carrying wire and a solenoid.

Explain uses of magnets and electromagnets.

Understand and describe that a current carrying conductor w h e n p l a c e d i n s i d e a magnetic field experiences a force.

Describe factors that affect the force on a current carrying c o n d u c t o r p l a c e d i n a magnetic field.

State and explain Fleming's left hand rule.

Describe the construction and working of an electric motor.

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PHYSICS SCIENCE UNIT-2 - NIMS Dubai · The CBSE has introduced the CBSE-i curriculum in schools...

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