grade7 unit p.2- electrostatics grade 7grade7 unit p.2- electrostatics - 11 - objectives: 1-know...

Grade7 Unit P.2- Electrostatics

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Grade 7

Electrostatics


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Curriculum standards: 18.1-18.3

Objectives:- 1-Know that electrostatic charges are caused

by friction when an insulator is rubbed.

.٣ؼشف ا اشضخ اسبخ تت ػذب ٣ضذث اصتبى غ بدح ػبصخ 2-Know that there are two types of charge,

positive and negative. ٣ؼشف ا بى ػ٤ اشضبد ارجخ اسبجخ

You may have seen a balloon stuck to the wall or ceiling or received a

small shock when touching a car door, or heard a crackle when taking

off your clothes. To understand any of these you must know the

Key Words:

Static

electricity

اشثبء

اسبخ

Charge شضخ

Friction اصتبى

Attract تزبرة

Repel تبكش

Positive رت

Negative سبت


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structure of an atom. هذ ٣تصن اجب ك٢ اسوق هذ تسغ صد خشخشخ ػذب تس ثبة

اس٤بسح ل زح اظبشح ٣زت ؼشكخ تش٤ت ازسحAtoms are one of the smallest particles in Nature. Atoms have three

basic parts.

Electron: atomic particles with a negative

electric charge. ( - )

Proton: atomic particles with a positive

electric charge. ( + )

Neutrons: atomic particles with no charge.

:ازسح تت حالث ارضاء ٢ ازسح ٢ اصـش رضء ك٢ ابدح

رضء ازسح ٣ض شضخ سبجخ:االتش

رضء ازسح ٣ض شضخ رجخ:اجشت

رضء ازسح ال٣ض شضخ:ا٤تش

Most objects are neutral, that means they have no charge. .(التض شضخ) تؼبدخ ااد اطج٤ؼ٤خ

If you rub a balloon with your

clothes the balloon becomes charged

and if you put the balloon near your

hair it will attract it. ػذ صي ثب ثالثسي ٣صجش اجب شض، ػذ

.توش٣ت اجب شؼشى ٣و ثززث

Some materials gain electrons and some lose electrons.

Material that loses electrons when it is rubbed becomes positively

charged.

Material that gains electrons when it is rubbed becomes negatively

charged. اتشبد ثؼط ااد ات٢ تلوذ اتشبد ػذ االصتبى تصجش راد شضخ رجخ اب ااد ات٢ تتست .

.ػذ االصتبى تصجش راد شضخ سبجخ

How do electrical charges act on each other?

We find that:

Like electric charges repel

Unlike electric charges attract. .اشضبد اتشبث تتبكش اشضبد اختلخ تتزبرة


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Unlike charges attract

Like charges repel

Insulators and Conductors ااد اؼبصخ ااد اصخ

An insulator is a material that resists electrons to pass through it.

. خالبشس االتشبد توب اد اؼبصخ ٢ ااد ات٢ ال

A conductor is a material that allows electrons to pass through it

more easily. اد اصخ ٢ ااد ات٢ تسش ثشس االتشبد خالب

Conductors Insulators

Water Glass

Skin Rubber

Metals Plastic

+ -

- - + +


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Induced Charges صج اشضبد If a material has an electric charge it can

Make or induce an electric charge on the surface of a material close

by without touching the materials.

.رس اخش ارا اهتشة س شض ا ٣شض٣ ذ

Worksheets

Q1-Decide which charges will attract and which will repel:

:اختش ك٢ ا١ صبخ ٣ضذث تزبرة ك٢ ا١ صبخ ٣ضذث تزبرة ك٢ االت٢

Q2- What will happen if a material has an

electric charge was but near on the surface

of a material without touching the materials?

ؿ٤ش برا س٤ضذث ارا ظغ رس شض ثبوشة رس اخش

شض؟

.........................................................................................

.......................................................................................

..................................................


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Q3- Explain why when you comb your hair in dry weather, your hair

sometimes sticks to the comb. كسش١ برا ٣تصن شؼشى ثبشػ ػذ تسش٣ضخ ثشػ ثالست٢٤ ارا ب اشؼش ربف؟

……………………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………………………

Q4- Which of the following is an insulator? أي المواد التالة من المواد العازلة؟

a. Iron.

b. Plastic

c. Aluminum

d. Copper

Q5- Saif hung a small plastic ball (ball A) on a

nylon thread and charged it negatively.

هب س٤ق ثتؼ٤ن شح ثالست٤٤خ شضخ ثشضخ سبجخ ثخ٤ػ اب٣

a) Describe one way that he could have used

to charge it. ارش١ اصذ اطشم ات٢ ٣ شض اشح ثب

He can charge the ball by....................

b) He has a second ball (ball B) on the end of a straw that he has also

charged. He brings ball B near to ball A, which is repelled. What

is the charge on ball B? Explain your answer

كب ٢ شضخ اشح . اال٠، صذث ث٤ب تبكشارا ب ذ٣خ شح حب٤خ شضخ ظؼب ثبوشة اشح

اخب٤خ؟ كسش اربثتي

Ball B has ......................charge because........................

............................................................................

............................................................................


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Q6- Complete the following: :ا٢ ب ٢٣

a- When some negative charges move out of a material it will

become…………………………………… charged.

.الشحنة..................تصبحعندما تتحرك بعض الشحنات السالبة الى خارج المادة فإنها

b- When some negative charges are added to a material it will

become ……………………………………charged.

.الشحنة........................عندما تضاف بعض الشحنات السالبة للمادة فإنها تصبح

c- Materials that allow electrons to pass through them are

called…………………………………….

.........................المواد الت تسمح بمرور االلكترونات من خاللها تسمى

Q7- Use the picture to answer the following

question. من الصورة المقابلة عن االسئلة التالة اجب:

1- Do the balloon and the hair have same or

opposite charges?

هل حمل البالون وشعر الفتاة نفس او عكس الشحنات؟

…………………………………………………..

2- Explain your answer. اجابتك فسر

……………………………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………………………….


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Curriculum standards: 18.2-18.4

Objective: Demonstrate the use of a Gold- Leaf Electroscope. ٤ق ٣ؼ ابشق اشث٢

Gold- Leaf Electroscope

This instrument can be used to tell whether an

object is charged, ز االداح ٣ ا تؼب ارا ب ازس

شض

the metal cap is connected to a metal rod a

strip of very thin metal (the gold leaf).This

gold leaf is hinged at the top so it can move. اـطبء اؼذ٢ ص ثؼد ؼذ٢ ثب٣ت شش٣ضت٤ ؼذ ازت

.ؼوت٤ هبثخ ضش

Key Words:

Gold- Leaf

Electroscope

ابشق اشث٢

ر١ اسهخ ازج٤خ

Metal Cap ؿطبء ؼذ٢

Metal Rod ػد ؼذ٢

Gold Leaf

سهخ رج٤خ


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Experiment1: اتزشثخ

Rub a polythene strip (to charge it with

negative charges) and bring it close to but not

touching the cap of the electroscope.

ظؼ هش٣ت سطش ابشق اشث٢ (ثالست٤ي) صي ػد ث٢ اح٤٤

The negative polythene induces charges in the

electroscope by repelling negative electrons

down to the metal rod and the leaf, because like charges repel each

other.

The golden leaf is repelled and lifted. اؼد اسبت سف ٣شض ابشق اشث٢ ثشضخ سبجخ ص٤ج االتشبد اسبجخ ستتو ؼد اؼذ٢

. ا٠ شش٣ضت٢ ازت كتتبكش الب ٣ضال لس اشضخ

Experiment2: اتزشثخ

Charge a polythene strip and then touch the

metal cap of the electroscope with it.

Some of the negative electrons moved from

the polythene to the electroscope where they

spread out over all the metal parts and made

the leaf rise by repulsion.

اشض اج٤ب٣خ٤ س٤شض سطش ابشق اشث٢ ح تتشش اشضخ اسبجخ ز٤غ ارضاء اؼد

.ابشق اشث٢ ك٤زؼ شش٣ضت٢ ازت تتبكشا اخش


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Worksheet

1- Complete the following:

a) To detect the electrostatic charges we can use

.................

...................الشحنات الكهربة نستخدم للكشف عن

b) When the electroscope is charged, the golden leaf

is…………………………………….

............................. اذا كان االلكتروسكوب مشحون فإن ورقة الذهب

c) When the charges are removed from an electroscope (it

becomes not charged) the golden leaf is………………………………….

..............فإن ورقة الذهب( صبح غر مشحون)عند ازالة الشحنة عن االلكتروسكوب

- Draw the gold leaf of the electroscope in each one of the following

electroscope: الذهب ف الحاالت التالة ةارسم ورق


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Objectives: 1-Know that lightning is an electrical discharge caused by a static

charge that results from friction between moving air masses, and

that it can be dangerous. .خطشحاجشم شضخ لشؿخ تضذث ثسجت االصتبى ث٤ ت ااء ٣ ا ت

2- Demonstrate the use of Van de Graff generator.

شبذح غش٣وخ ػ ربص الب درشاف

Key Words:

Lightning اجشم

Lightning

conductor بؼخ اصاػن

Electric

discharge اتلش٣ؾ اشث٢


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Electrical discharge: اتلش٣ؾ اشث٢

When you walk across a carpet and then you reach for a metal

doorknob, you feel an electric shock.

ػذب تش٢ ػ٠ سزبح تس وجص اجبة اؼذ٢ كبي تشؼش ثصذخ شثبئ٤خ

Do you know what happens? تؼ برا صذث؟

As you walk, on the carpet you rub it with your shoes negative

charges move from the carpet to your shoes. Then negative charges

spread out over your skin and when you put your hand close to the

metal doorknob. When negative charges move from your hand to the

doorknob. And that is called electric discharge.

ػذب تش٢ ػ٠ اسزبد ٣ضتي اضزاء اجالست٢٤ ثبسزبد كتتو اشضبد اسبجخ اسزبد ضزاء ح

تتشش ك٢ ازذ ػذ ظغ ٣ذى ثبوشة وجط اجبة اؼذ٢ تتو اشضبد ٣ذى ا٠ وجط اجبة

.اتلش٣ؾ اشث٢زا ٣س٠

Lightning is an example of an electric

discharge اصذ اخخ اتلش٣ؾ اشث٢ اجشم


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When a storm cloud develops, strong winds move upward through the

cloud and rub against large rain drops and hail stones. This rubbing

causes development of charged particles in the cloud.

Positively charged particles collect at the top of the storm cloud.

Negatively charged particles collect at the base.

The size of the different charges in each part of the cloud may

become so large that lightning is produced between them.

تتطس ؿ٤خ ػبصلخ كب اش٣بس او٣خ تضتي ثوطشاد اطش زا االصتبى ٣شض رض٣ئبد اـ٤خ ػذب

اشضبد ارجخ تتزغ ك٢ اػ٠ اـ٤خ اشضبد اسبجخ تتزغ ك٢ اسل اـ٤خ زا الشم ك٢ اشضبد

.٣سجت تلش٣ؾ شث٢


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Lightning Conductor اصاػن حبغ

Electrostatic charges discharge most easily at a specific point. اتلش٣ؾ اشث٢ ٣ضذث ثسخ وطخ

A lightning conductor is a metal rod that may be attached to the

top of a tall building. If lightning strike it hits the conductor rather

than the building, and the current of electricity passes down the

metal strip to the ground.

اصاػن ػد ؼذ٢ ٣ظغ ػ٠ اػ٠ ج٠ ػذب ٣عشة اجشم كب اؼد اؼذ٢ ٣ص حبغ

.اشثبء خال شش٣ػ ؼذ٢ ا٠ االسض

Van de Graff generator

In 1931 Robert Van de Graff invented a

machine which produced a huge charge of

static electricity the machine is called a

Van de Graff generator.

It is a hair raising experience. If someone in the class has soft dry hair,

ask them to stand on a thick sheet of polythene (to insulate them from

earth) while they touch the dome.

Observe what happens.

اختشع سثشد كبذ٣زشاف ربص ٣ؼ ػ٠ اتبد شض سب ج٤شح ٣س٠ ازبص كبذ٣زشاف كؼذب 1931ػب

.شؼش٣وق اس ػ٠ س ث٢ ا٣خ٤ ػبص ػ االسض صت٠ التلشؽ اشثبء تس ازبص ك٤وق ا


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Worksheet

Answer the following questions: ارت ػ االسئخ اتب٤خ

1- How lightning is produced in storm clouds? Draw a diagram below. be

sure to label it correctly.

، اسس٢ خطػ ٣خ ٤ل٤خ صذث اـ٤خ ظؼ٢ اج٤ببد ػ٣٤ضذث اجشم ك٢ اـ٤خ ٤ق ………………………….……………………………………………………………………………………………………………….

2- How can we prevent strike of lightning to a tall building?

٤ق ٣ صب٣خ اجب٢ اجشم؟………………………………………………………………………………………………………………………………………….

3- Why you should stand on a thick sheet of polythene when you touch

Van de Graff generator?

برا ٣زت ػ٠ اشخص ا ٣وق ػ٠ شش٣ضخ ث٢ ا٣خ٤ ػذب ٣س ربص كبذ٣زشاف…………………………………………………………………………………………………..……………………………………….

grade7 unit p.2- electrostatics grade 7grade7 unit p.2- electrostatics - 11 - objectives: 1-know...

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