grade 9 unit p.2 electricity & energy electricity and energy · 2010. 12. 28. · grade 9 unit...

Grade 9 Unit P.2 – Electricity & Energy

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Electricity and Energy


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Standards: 22.1: Distinguish alternating current (AC) from direct current (DC) and know

why household electricity is AC and not DC.

22.2: Know that household electrical energy comes from a cell which generates

DC or from an electrical power generator which generates AC.

22.3: Know how AC is produced commercially using a generator that is usually

driven by a steam turbine, a gas turbine or a diesel engine, or by moving water

from a dam.

Key Words

Current اهخبر Alternating يخردد Household يزه Generator يهد Dynamo دبي Ampere ايتر

Objectives:

1- Distinguish alternating current (AC) from direct current (DC).

2- Know why household electricity is (AC) not (DC).

3- Know how (AC) is produced commercially using a generator that is

usually driven by a steam turbine, a gas turbine or a diesel engine, or

by moving water from dam.


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:Introduction: يلديج

Electrical energy can be generated by a variety of methods.

A battery produces electrical energy very effectively, but electric power plants

provide most of electrical energy used every day. ؾطبد ر١ذ اىشثبء از رفش أغت اطبلخ اىشثبئ١خ ض اجطبس٠بد: ثؼذح ؽشق ٠ى ر١ذ اطبلخ اىشثبئ١خ

. اغزخذخ

When a conductor is connected to two oppositly charged objects, electrons will

flow through. The flow of electrons through a conductor is called

electric current. The number of electrons flowing determines the amount of

electric current. ي ىزشبد خالؽشوخ اإل ٠غ. اط اىزشبد داخ شدعف ػذ رط١ ط وشثبئ ثشؾبد خزفخ

. رش خالي اط از اإلىزشبدثؼذد ؽذد و١خ از١بس اىشثبئدوشثبئ اير١بس ايط وشثبئ ة

Electric Current has two types: اهجيبر اهنهرببئي وعب

1- Direct Current: اهجيبر اهيببشر

Current that always flows in the same direction is called Direct Current (DC)

Figure 1 below shows the positive and negative poles of a battery connected to

a wire. The wire is connected to a small lamp. The electric current from the

battery keep the lamp lit. Notice that the current flows from negative pole to

the positive pole of the battery. The current flows in one direction. All batteries provide direct current.

عجخ اغبجخ أدب األلطبة اي ٠1ج١ اشى . از١بس اجبششرذفك دائب ف فظ االرغب ٠غ راي ر١بساي

.اجطبس٠خاز١بس اجبشش ٠خشط امطت اغبت . وشثبئ ظجبػػبءح إل اطخ ثغه

2- Alternating Current: جرددهجيبر اهىا

Current that changes direction at the regular rate is called

Alternating Current(AC).The type of electricity used in homes is alternating

current. Most of electricity that used in everyday life comes form alternating

current- not from direct current. There is practical reason to use alternating

current. ١ظ سددذف ابصي از١بس ا از١بس اغزخذ. سددزظخ از١بس اذ ثظسح از١بس از ٠غ١ش ارغب

.اجبشش


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Wires carrying direct current become hot. An electric power plant sends

electricity over long cables to reach your home. The heat from large amounts of

direct current would damage the cables. As a result, the power plant can’t use

the direct current to transport the electricity. Alternating current produces

less heat and it is safer. This is the main reason alternating current is used.

اغزى١ إ اىشثبءر١ذ اي ػذب رجؼش ؾطبد .٠زظ ؽشاسح عخاألعالن از رؾ ر١بسا جبششا د

٠ظجؼ ؽشاسح ال ٠زظ از١بس ازشددإب ,األعالن رظشف ػب١خ سح اجؼضخ از١بس اجبششرى و١خ اؾشا

.از١بس ازشدد٠غزخذ زا اغجت .أبب أوضش

Most household appliances use alternating current. However, some appliances

need direct current. A built-in converter in these appliances changes

alternating current into direct current. رغزخذ األعضحثؼغ أ إالاض١خ رغزخذ ر١بس زشدد األعضح ؼظ أ ثبشغ

. جبشش إ زشدداي ؾالد زؾ٠ از١بس ػ األعضحر رؾز اجبشش ز ر١بس

The electric current can be measured by connecting an

ammeter across the terminals of the cell.

(See Figure 2). (.أ١زش)اغبص از ٠م١ظ از١بس اىشثبئ ٠2ج١ اشى

Figure 2

Why Alternating Current is used? لمارا يسخخذم الخياس المخشدد؟

Figure 1


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The SI unit of current is the ampere (A), which is

sometimes called (amp). The symbol for current is

letter (I). (I) ثبؾشفاىشثبئ سض ز١بس. أج١ش م١بط از١بسح اؽذح اغزخذ

Most electricity is generated in power stations. If you ride a bike with a

dynamo, you’re the power station, its your energy that drives the dynamo to

make the lights work.

رشوتى إرا وذ ؽبلخ٠ز ر١ذ ؼظ اطبلخ اىشثبئ١خ ف ؾطبد ر١ذ اي رغؼ داي نة طخاطبلخ اخب إبؾطخ ر١ذ اىشثبء ، ذفأدساعخ غ د٠ب ،

.األػاء شؼ٠ذ وشثبء د٠ب اي

As you’re cycling along, your back wheel turns the

knob at the end of the dynamo, which makes

electricity to lit the lights. The energy you supply is

changed into electrical energy. This an example of a

simple generator.

اطبلخد٠ب ، ايمجغ ف ب٠خ اي سنرؼ اخف١خ ػغخاي، حسوت اذساطدػذب ػ ذ وشثبئ از رؾشن ثب اؼغخ رزؾي إ ؽبلخ وشثبئ١خ زا ضبي

.ثغ١ؾ Inside a Power Station: داخل يحطت جوهيد اهنهرببء A power station has much bigger generators than a bicycle dynamo.

The generators in the photo are turned by moving water - it’s a hydroelectric power station. The water spins the generators, and a lot of electricity is

produced. (حوشبئ ؽبلخ ؾطخ)رذاس ثبء زؾشن . 5اشى .رؾز ؾطبد ر١ذ اىشثبء ػ ذاد اوجش اذساعخ

. داذا ثزذ٠ش سحرذ ؽبلخ وشثبئ١خ وجف

Figure 3

Figure 4

جوهيد اهنهرببء


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Motors and Generators : اهيحرنبث واهيوهداث A generator or a dynamo is similar to an electric motor, working in reverse. You

can even make a motor work like a generator. .٠ؼ ثبؼىظ ى وشثبئ اذ أ اذ٠ب شبث رس

A motor has a coil which

turns in a magnetic field. You

supply electrical energy, and

the motor changes it to

kinetic energy and turns.

A generator has a coil which you

turn in a magnetic field. You supply

kinetic energy, and the generator

changes it to electrical energy to

light the lamp.

Figure 5

Figure 6

. غبؽ١غغبي ف رس اىشثبئ ف ٠ذس ا.ؽشو١خإ ؽبلخ رؾي اطبلخ اىشثبئ١خ

. غبؽ١غ غبيف اذ اىشثبئ ف ٠ذس .٠ؾي اطبلخ اؾشو١خ إ ؽبلخ وشثبئ١خ


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Inside a Coal-Fired station powered (by steam):

(اهبخبر)ببهفحى يحطت جوهيد اهطبكت

When the coal is burned, heat energy is transferred to water in the boilers. A

boiler is like a giant kettle, producing very hot steam. The steam rushes along

pipes to turn the turbines. These make the generator spin round, generating

electricity. . غال٠خ ػاللخ رزظ ثخبس ؽبس عذا ٠شج اشع, إ ثخبس ػذ ؽشق افؾ اطبلخ اؾشاس٠خ رؾي ابء ف اشع

.. اىشثبءرسث١بد از رذ٠ش اذ ز١ذ اي٠ش زذ أبث١ت خالي اجخبس اؾبس ٠ذفغ

Figure 7


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Fill in the blanks below: 1. The flow of electrons through a conductor is called______________

شرب االهنخربح خالل اهيصل شيى 2. Current that change direction at a regular rate is called

__________current اهخبر اهذي غر اخجب تيعدل يخظى

3- When charges always flow in the same direction, there is a(n)

___________current. -----------------------------معديب خخدرم ااهشدبح ف اخجب ادد شف ن ب

4- A battery is a source of _____________________current -----------------------------------------------اهتطبرج يصدر هوخبر

5- The type of electricity supplied by electric power plants to our homes

is ___________ ---------------------------------------ع اهخبر اهيشخخدى ف اهيبزل

6- A______________ converts kinetic energy into electrical energy دل اهطبكج اهدرنج اه طبكج نرتج ---------------

7- A_______________converts electrical energy into kinetic energy ث اه طبكج درنج دل اهطبكج اهنرت ---------------

8- The SI unit used to measure current is _______________________ --------------------------------ددث كبس اهخبر

9- The device used to measure electric current is _________________ -------------------------------هلبس اهخبر اهنرت اهجبز اهيشخخدى

10- The symbol for current is _____________________________ -----------------------اهريز اهيشخخدى هوخبر

1. Define Electric Current: ػشف از١بس اىشثبئ

_____________________________________________________

__________________________________________________

2. Compare :between an Alternating & Direct current first; then between

an Electric Generator & an Electric Motor . لبس


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Alternative Current Direct Current سدداز١بس اذ ز١بس اجبششا

Electric Generator اذ اىشثبئ Electric Motor اؾشن اىشثبئ

3. Describe two ways of generating electricity. ز١ذ اىشثبء طف ؽش٠مزب

_____________________________________________________

___________________________________________________

4. Why is it better and safer to use AC at homes.

يف ابص أبب أوضشأفضل ازشدداعزخذا از١بس ٠ؼزجش برا

_____________________________________________________

_____________________________________________________

_________________________________________________


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Standards:

21.1 Understand the concept of electrical potential between two points

on a circuit and know that it is measured in volts using a voltmeter

21.2 Know that the total potential drop around a circuit is equal to the

sum of the potential differences across each series component.

21.3 Recognize that the potential difference across a component is a

measure of the energy carried by the current and transferred by the

component, and that a potential difference only occurs in a circuit when a

component offers some resistance to the flow of the current.

Key Words

Potential difference فشق الجهذ

Electromotive force الكهشبائيت الذافعتالقىة

Voltage الجهذ

Volt الفىلج

Objectives:

1- Understand the concept of electrical potential between two

points on a circuit.

2- Know that it is measured in volt using a voltmeter.

3- Know that the total potential drop around a circuit is equal to

the sum of the potential differences across each series

components.


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Figure 1

When you wake up in the morning, you reach up and turn on the light

switch. The light bulb is powered by moving charge. How does charge move

through light bulbs? And what causes the charges to move?

The cell above is pushing out electrons. The electrons repel each other, so, like

the coils of compressed spring, they have potential energy. As the electrons

slowly flow round the circuit, they transfer energy from the cell to bulb. The

energy is radiated by the hot filament.

، ض فبئف اضجشن ثؼؼب اجؼغ رزبفش غاإلىزشبد . رذفغ اىزشبد اخ١خف اشى اػؼ أػال الؽظ أ

رشغ ف. اظجبػ إؽبلخ اخ١خ اي، فئب رم ف اذائشح ػذ رذفك االىزشبد ثجؾء. اؼغؽخ ، ب ؽبلخ وبخ

.اغبخخفز١خ اظجبػ اطبلخ PD (Voltage) across a cell: عبر خويت ( اهجهد)فرق اهجهد

A cell normally has a voltage marked on it. The higher its voltage, the more

energy it gives to the electrons pushed out.

.ثض٠بدح اغذ ، رضداد ؽبلخ االىزشبد. خ١خ ب عذ ىزة ػ١بو

The scientific name for voltage is potential difference (PD).

.اؼ غذ فشق اغذ العا

Electrons

return to cell

Electrons

transfer

electrons to bulb

Cell gives electrons

potential energy

Electrons lose potential energy:

energy radiated


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افشق ف اطبلخ ى ؽذح شؾخ (: فشق اغذ)اغذ

. ث١ مطز١ ف غبس از١بس خاشؼ رزؾشن ػذب

(PD) can be measured by connecting voltmeter

across the terminals of the cell.

. خ١خايفز١زش ػجش اي ثزط١اغذ فشق ٠مبط

The SI unit of potential difference is the Volt

.اؽذح اغزخذخ فشق اغذ افذ

If the PD across a cell is (1 Volt), then (1 Joule) of potential energy is given to

each coulomb of charge. If the PD across a cell is (21 Volts), then (21 Joules) of

potential energy are given to each coulomb of charge … and so on.

إرا وب فشق . اطبلخ اىبخ ى شؾخ( عي 1) ؽبلخ ػط فب، ( فذ 1)ق اغذ ػجش اخ١خ إرا وب فش

...ىزا. اطبلخ اىبخ ى شؾخ( عي 21)، عزؼط ( فذ 21)اغذ ػجش اخ١خ

A cell produces its highest PD when not in a circuit and not supplying current.

This maximum PD is called electromotive force (EMF) of the cell. When the

current is being supplied, the PD drops because of energy wastage inside the

cell. For example, a car battery labeled “12V” might only deliver )9V( when being

used to turn a starter motor.

امح اذافؼخ ) ب ٠غ . ال رؼط ر١بسا زظخ ثذائشحغ١ش ػذب رىسق اغذ ثأػ غز٠بر اخ١خ رزظ ف

ثطبس٠خ , ػ عج١ اضبي . ػذ عش٠ب از١بس ، ٠خفغ فشق اغذ ثغجت إذاس اطبلخ داخ اخ١خ. خ١خ( ٠خ اىشة

.فذ ػذ رشغ١ اؾشن( 9) فذ ف ؽ١ اب رفش( 12)اغ١بسح ىزة ػ١ب

Voltage (or PD): is the difference in energy

per unit charge as a charge moves between

two points in the path of a current.

Figure 2


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PDs around a circuit: فرق اهجهد حول دائرة

As with an Ammeter, the Voltmeter must be connected the correct way

round (+ to +).

+(إهى )+ اهصددج نيب يضخ تبهشنل نيب اهدبل ف األيخر جة خصل اهفهخيخر تبهطرلج

What is the reading on your voltmeter? اهفهخيخر؟ يب كراءث

Reconnect the voltmeter (always in parallel, across a component) to find the PD

across the other lamp. .اهجد عتر اهيصتبح األخرهخلس فرق ( دائيب عوى اهخازي)أعد خصل اهفهخيخر

Then use your voltmeter to find the PD across the cell. .هخلس فرق اهجد عتر اهخوج اهنرتج( دائيب عوى اهخازي)ذى اشخخدى اهفهخيخر

What do you notice about your three readings? كبر اهلراءاح اهذالد؟ يبذا خالدظ؟

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

The total voltage across the lamps equals the voltage across the cell.

.غع اغذ خالي اظبث١ؼ رغب اغذ ػجش اخ١خ

Quick Activity شبؽ Using a voltmeter: اعزخذا افز١زش

Connect cell to two lamps in series as shown in figure 3.

3و دائشح وشثبئ١خ خ١خ وشثبئ١خ ظجبؽ١ ط١ ػ ازا وب ػؼ ثبشى سل

Then connect a voltmeter across each one of the lamps as shown in the

figure, and then take the reading.

. وب ػؼ ثبشى عغ لشاءح و عبص ػجش و ظجبػ ط عبص افز١زش


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In the circuit – figure 3, the electrons flow through two bulbs. They

loose some of their potential energy in the first bulb and the rest in

the second. In total, all the energy supplied by battery is radiated by

the bulbs almost none is spent by the connected wires.

ظجبػأي ف لزبرفمذ ثؼغ ؽب ثبزب.ثبؽ١اض خاليف اذائشح رذفك االىزشبدد الؽظػ ٠غبس اشى

رزوش رمش٠جب ؽبلخ رغزهاألعالن فال ، إبرمش٠جب ثبؽ١اض٠غزخذب ثطبس٠خ اي، و اطبلخ از رفشب اجبل ف اضب

Like the battery, each bulb has a PD across it.

ى ظجبػ فشق عذ ض اجطبس٠خ

The second diagram shows the same circuit with voltmeter connected across

different sections (the voltmeter do not affect how the circuit works). The

readings illustrate a principle which applies in any circuit امشاءاد رػ١ؼ اجذأ از ٠طجك .خزفخذائشح اا غ افز١زش زظال ػجش أعضاء فظ اذائشح الؽظ ػ ١٠ اشى

(فشق اغذ خالي اجطبس٠خ= غع فشق اغذ خالي أعضاء اذائشح اخزفخ ) دائشحف أ

Moving round a circuit, from one battery to the other, the

sum of the PDs across the components is EQUAL to the PD

across the battery.

Figure 3


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Cell in series: ازاػ رط١ اخال٠ب

To produce a higher PD, several cells can be connected in series (in line) as

shown in figure 4. The word battery really means a collection of joined

cells, although it is commonly used for a single cell as well.

غػخ اجطبس٠خ رؼ . 4وب ج١ ف اشى ػ ازا ، ٠ى رط١ ػذح خال٠ب غذفشق إلزبط أػ

. حازظ اخال٠ب

Choose the correct answer اخجر اإلجببت اهصحيحت

Figure 4


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What is the potential difference between two points in a circuit called?

يبذا شي فرق اهجد ت لطخa. resistance يلبيج b. current خبر c. voltage جد

d. charge شدج

Which letter is used to represent voltage as a symbol? يب اهدرف اهيشخخدى هوخعتر ع اهجد؟

a. G b. C c. V d. I

What happens to the electric current if the voltage becomes larger? يبذا ددد هوخبر اهنرت عد زبدث فرق اهجد؟a. The current decreases. لل اهخبر

b. The current increases. زداد اهخبر c. The current stays the same. ال خغر اهخبر

d. No current will flow.خكف اهخبر

Fill in the blanks: اهفراغبث أيلء

A. The scientific name of voltage is __________ & it is defined as

_________________________________________________

----------------------------٠ؼشف ػ ا -------- االع اؼ غذ-------------------------------------------------------

B. The SI unit of voltage is ________________.

----------------------------------ؽذح ل١بط اغذ

C. To measure voltage a ____________________ is used.

---------------------------------م١بط اغذ ٠غزخذ

D. As voltage increased , the provided energy will ------------.

,-----------------------------عففب اطبلخ ,اغذ فشق ثض٠بدح


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Answer the following questions

1. What is Electromotive force? ب امح اذافؼخ اىشثبئ١خ

_________________________________________________________

_______________________________________________________

_________________________________________________________

_______________________________________________________

2. What is the difference between the two circuits in voltage? ؟ ازب١خسثبئ١خ اذائش اى ف اغذ فشقاؽغت

___________________________________________________________

___________________________________________________________

___________________________________________________________

_________________________________________________________ ___________________________________________________________

___________________________________________________________

___________________________________________________________

_________________________________________________________


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3- Complete the circuit below as follow أنيل اهدائرث أدب نيب و a- The empty circle represent a meter . Add the correct letter to show

which type of meter it is اهدرف اهذي يذل ذا اهجبز هولبس أضفاهدائرث اهفبرغج خدخي عوى جبز

b- What does it measures ? يبذا لس؟

----------------------------------------------------

c- Add a second meter to the circuit to show how you would measure the

voltage across the lamp جبز خر هلبس فرق اهجد ت طرف اهيصتبح أضف

d- What would you expect the reading on this meter to be ?

يب خكعم هلراءث اهجبز؟-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


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Standards:

21.4: Show the relationship between the voltage across a conductor and the

current flowing through it.

21.5: Know that electrical components have resistance that slows the flow

of electricity through them and that is measured in Ohms,

21.6: Calculate the resistance of a component knowing the current passing

through it and potential difference between its ends.

21.7: Know how the resistance of a wire depends on its diameter, length

and the material it from which it is made.

Key Words

Resistance اهيلبويت Ohm أوى

Omega أوييغب

Objectives:

1- Know that electrical components have resistance that slows the

flow of electricity through them.

2- Know that resistance is measured by Ohms.

3- Know how the resistance of a wire depends on its diameter,

length and the material it from which it is made.

4- Calculate the resistance of a component knowing the current

passing through it and potential difference between its ends.

Lesson 13


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When an electric current flows through a wire, the electrons are slowed

down a bit by the wire. The electric current meets a certain resistance from

the wire. .االىزشبداإلىزشبد رزجبؽأ ل١ال ثغجت اغه از ٠مب فئ خالي عه وشثبئ، دب ٠زذفك از١بس اىشثبئػ

RESISTANCE: is the opposition to the flow of electric charge (current). (.از١بس اىشثبئ)ح رذفك اإلىزشبد بغ امبخ

Resistance is measured in Ohms and is represented by a Ω , the Greek

letter omega. (.االر١ أ١غب اؾشف) Ω اؾشف ة از ٠شضؽذح أ رمبط امبخ ثبعزخذا

You can think of resistance as “electrical friction”. The higher the

resistance of a material is, the lower the current is inside the wire.

Therefore, if the resistance increases the current will decrease if the voltage is kept the same.

صجد ز١بس اىشثبئ ابس ف اغه ػذ وب صادد مبخ ابدح وب ل ا. ٠ى اػزجبس امبخ اؽزىبوب وشثبئ١ب

. فشق اغذ

An object’s resistance depends on: اهيلبويت جعجيد عوى

1- Material: وعيت اهيبدة Good conductors, such as copper, have a lower resistance. Poor conductors

such as iron, have a higher resistance.

Materials with low resistance are used to make wires and other objects that

are used to transfer electrical energy from place to place. .اطالد غ١ش اغ١ذح ض اؾذ٠ذ ، ذ٠ب مبخ أػ. اطالد اغ١ذح ، ض اؾبط ، ذ٠ب مبخ أل

رغزخذ ااد راد مبخ ل١خ ؼ األعالن غ١شب األش١بء از رغزخذ م اطبلخ اىشثبئ١خ ىب إ

.آخش

Figure 1


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2- Thickness اهسيم Resistance depends on the amount and shape of the material as well as

on the type of material itself. A wire that is thin has more resistance

than a wire that is thick. Think of how you have to work harder to drink

through a narrow straw than a wide one. A wire that is long has more

resistance than a wire that is short. Again, think of how much harder it

is to drink through a long straw than a short one . اغ١هط ا فبط اشف١غ أوضش مبخ . اط عهرؼزذ امبخ ػ

-3 Length: اهطول اط اط٠ ذ٠ مبخ أوضش امظ١ش

So, far you have learned about current, voltage and

resistance. But how are they related?

A German schoolteacher named George Ohm asked this

question. He determined that the relationship between

current (I), voltage (V) and resistance (R) could be

expressed with the equation shown below.

This equation is known as Ohm’s Law .

:ا٢ر١خاؼب عسط ا ػؼ اؼاللخ ث١ از١بس فشق اغذ امبخ ثبؼبدخ

** The figure 3 below shows the relationship between the (PD) and the (I) for

the same material (Important: Keep in mind the resistance is constant).

(.ثضجبد امبخ)٠ج١ اؼاللخ ث١ فشق اغذ از١بس اىشثبئ بدح 3اشى

Ohm’s Law: electric current is directly proportional to voltage and

inversely proportional to resistance. ٠زبعت ربعت ػىغ غ امبخاز١بس اىشثبئ ٠زبعت ربعت ؽشد غ فشق اغذ

Resistance (R) = PD across the wire (V)

Current through the wire (I)

Ohm (Ω) = Volt (v)

Ampere (A)

Figure 2


- 22 -

1. Define : resistance: ػشف امبخ

_______________________________________________________

_____________________________________________________.

2. Fill in the blanks below:

A. In an electric circuit; the flow of electrons are slowing down because of _________________________

ثغجت د٠ؾذس رجبؽأ غش٠ب االىزشب :ف دائشح وشث١خ

.

B. If the voltage is constant ; decreasing the resistance , will----------

the current از١بس -----------------ػذ صجبد فشق اغذ ؛ رم١ امخ عف

C. Resistance is measured in __________________________________

-------------------------------------- ؽذح ثبعزخذارمبط امبخ

D. The higher the resistance of a material is, the lower the_________

----------------------------------- قم كهما, انسهك مقاومة رادت كهما

E. Good conductors have a(n) ______________________resistance

-----------------------------------------اطالد اغ١ذح رى مبزب

Figure 3


- 23 -

3. Describe the factors that affect resistance. اؼا از رؤصش ػ امبخ أذنر

-----------------------------------------------------------------------------------

-----------------------------------------------------------------------------------

-----------------------------------------------------------------------------------.

4. Why are high resistance materials useful in light bulbs?

؟ اظبث١ؼ طبػخ برا رغزخذ ااد راد امبخ اؼب١خ ف -----------------------------------------------------------------------------------

-----------------------------------------------------------------------------------

----------------------------------------------------------------------

5. Explain, step by step , how to calculate the amount of current (I) that will

go through the resistor in this circuit below. اششػ خطح ثخطح و١ف ٠ز ؽغبة از١بس اىشثبئ خالي امب ف اشى ازب

_______________________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________


- 24 -

6. What is the value of this resistor,

in Ohms )Ω(?

؟(اعزخذ ا) حب ل١خ امب

________________________________

________________________________

________________________________

________________________________

________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________

7-A resistor has a steady resistance of 8 Ω :

Ω 8 مبخ لذسبمقاوو نه

a- If the current through the resistor is (2A), what is the PD across it?

,(2A)٠غب وب از١بس إراب مذاس فشق اغذ

----------------------------------------------------------------------------------------------------------------

-

b- If the PD falls to (6V), what is the current?

، فب ل١خ از١بس؟ ,(6V) وب فشق اغذ إرا

---------------------------------------------------------------------------------------------------------------

8 -The wires shown below are made of copper and have the same temperature.

Which wire should have the lower resistance? Explain your answer.

A B

أ٠ب مبخ أل غ روش اغجت؟ . األعالن اػؾخ ظػخ اؾبط ب فظ دسعخ اؾشاسح

------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------

8- Search : use the internet to find out “ What are superconductors?”


- 25 -

Standards:

22.6: Be familiar with household ring main circuits, with the common dangers

of household electricity, and with the purpose and operation of safety devices

such as fuses, circuit breakers and the earth wire.

Key Words

Fuses منصهشال

Ring main الذائشة الشئيسيت

Objectives:

1- Know that household electrical energy comes from an

electrical power generator which generates AC.

2- Know the operation of safety devices such as fuses, circuit

breakers and earth wire.


- 26 -

Figure 1 : Shows how electric current is transformed on its way to your

home.

Power of the AC mains is generated in power stations, transmitted (sent)

through long – distance cables, and then distributed to consumers.

When you plug a kettle (or other appliance) into main socket, you are

connecting it into a circuit.

The supply voltage is about 230V for main sockets and other household

circuits.

Main current is alternating current (AC). It flows backwards and

forwards, backwards and forwards ... 50 times per second when the main

frequency is 50 hertz (Hz).

رشع اطبلخ خالي وبثالد ص " ٠ز ر١ذ اطبلخ اىشث١خ ف ؾطبد ر١ذ اطبلخ از رزظ ر١بسا زشددا

.ؽ٠خ اغبفخ ، ص رصع ػ اغزى١

.وشثبئ١خ رط١ إ دائشح ٠زف امجظ اشئ١غ ، ( أ غ١شب األعضح)ػذ رط١ غال٠خ

.دائش اض١خ األخشاياشئ١غ١خ مبثظ ( V 230 )از١بس اىشثبئ إذاد

رشدد اي ٠ى شح ف اضب١خ ااؽذح ػذب ٠50زذفك إ اخف األب سدد ازاشئ١غ از١بس اذ از١بس

.شرض 50اشئ١غ


- 27 -

Household Wiring: Here is a simplified diagram of a modern household circuit. It is in two parts:

A. The lighting circuit. B. Ring main. : عضئ١ . اؾذ٠ضخ اض١خ ائشذيسع رخط١ط جغؾ اشى أدب ٠ػؼ

.ح اشئ١غ حاذائش -. سح اإلػبءحادا -

L and N in the Diagram 1 below refer to the Live and Neutral wires coming

from the power station. The third wire E is connected to Earth.

The Live wire is the most dangerous- the mains voltage may easily kill you.

The Neutral wire also carries the current, but because it is earthed back

at the power station; its voltage is usually not as the live wire.

The Earth wire is for safety and only carries a current when there is

fault, so that a fuse melts.

= L امبدخ ؾطخ ر١ذ ؽ١خأعالن

(.خطشح ازؼشع لذ ٠مز) اىشثبء

N = رؼبدخ امبدخ ؾطخااألعالن ر١ذ اىشثبء

= E ش إرااط ثبألسع غالخ عهاي

.ظشف١ ر١بس وشثبئ ف١ى ثبخطأ ٠زة ايThe electricity supply cables

into each house that contain a

live and neutral wire. At the

consumer unit (fuse box), these

wires are branched into several

parallel circuits for lights, and

mains sockets.

ؽ١خ زؼبدخ أعالنرط ,ششوبد اىشثبء

ف ؽذح اغزه رط . اغزه إ

راص إلػبءح ػ اطالد ثذائش رط١

.ح امبثظ اشئ١ظ

Diagram 1


- 28 -

Ring Main defined as: اذائشح اشئ١غ١خ رؼشف

Is a cable which begins and ends at the consumer unit with live, neutral and

earth wires each forming a long loop or “ring” around the house and the mains

sockets are connected to a ring main as shown in Diagram 1. ف ع١غ رشى ؽمخ ؽ٠خ از األسػ رؼبدخاي ؽ١خعالن اياأل اىبث از ٠جذأ ٠ز ف ؽذح اغزى١ غ

.1 رخط١طوب ػؼ ف اشع اي حاشئ١غ حإ اذائشاز١بس اىشثبئ لبثظأؾبء اضي ٠ز رط١

Safety Devices: أجهزة السالمت

1- Fuse: المنصهش

Is a thin tin wire included in

circuits as deliberate weak links

for safety, so that if a fault

occurs and too much current

flows, the fuse wire melts

before anything else is damaged

or fire starts.

, دائشايف ٠زاعذ عه لظذ٠ش سل١ك

ثزثب غالخ ، ره دػؼ١فخ ػغطالد

ف١غ ػذ شس ر١بس وشثبئ ػب ثبخطأ

.أ ؽش٠ك ؽذس أػشاس

2- Circuit Breaker: قاطع الذائشة

Circuit breakers help to make the electricity supply in your home safer.

It is an automatic safety switch. It cuts off the current if it gets too big.

. ٠مطغ از١بس اىشثبئ أربر١ى١ب ػذب ٠ش ر١بس ػب, أبب أوضش٠غبػذ ف عؼ اىشثبء

3- Earth Wire: سلك األسضي ال

If a fault develops in an appliance and a live wire touches the metal case, a large

current flows from the live wire to the earth wire and the fuse breaks.

This makes the appliance unsafe until the fuse is replaced.

ع١ش ر١بس وشثبئ ػب اغه اؾ ا عه األسع , ؽظ خطأ ف األعالن اؾ١خ الظ اظذق اؼذ إرا

. ظشزا ٠غؼ اغبص غ١ش أ ؾ١ رغ١١ش اي. ظشف١مطغ اي

Diagram 2


- 29 -

Do You Know

Many appliances have an earth connection. This is particularly important for

appliances with metal cases, including heaters and washing machines.


- 30 -

Look at the diagram to

the right. Explain what

is :L, N & E.

ػؼ برا أظش ا اشع ص N & L & E عى

----------------------------

----------------------------

----------------------------

----------------------------

----------------------------

----------------------------

----------------------------

----------------------------

----------------------------.

What is fuse? How does it work? ؟ و١ف ٠ؼ ب اظش

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

-----------------------------------------------------------------------------.

How do circuit breakers differ from fuses? .لبؽغ اذائشح اظشث١ فشقب اي

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

-----------------------------------------------------------------------------.

Why is the Earth wire important? ؟ ب أ١خ اغه األسػ

--------------------------------------------------------------------------------

------------------------------------------------------------------------------.


- 31 -

Standards:

22.8: Know that the unit of household electrical energy is the

kilowatt-hour and be able to work out the cost of running different

appliances from their power rating.

Objectives:

Know that the unit of household electrical energy is the kilowatt-hour.

Know how to work out the cost of running different appliances from

their power rating.

Key Words

Power انقذرة

Watt واط

Rate معذل

Appliances أجهسة

Convert حىلي


- 32 -

Electrical energy is used in many ways to do useful jobs, appliances such

as kettles, toasters, and mixers take energy from the supply and

transform it (change it into other forms). For example, appliances with

heating elements change it into thermal energy (heat). األعضح ض امذس اؾبض ، ف، ػذح بطرق ٠ز اعزخذا اطبلخ اىشثبئ١خ م١ب ثأػبي ف١ذح

ؽيرغخ١ داي ػ عج١ اضبي ، أعضح (. إ أشىبي أخشا رغ١١ش) اىشثبئ١خاطبلخ رؾيخالؽبد اي

(.اؾشاسح)إ اطبلخ اؾشاس٠خ اطبلخ اىشثبئ١خ

Power of the appliance in the home

Power: is The rate at which an appliance converts electric

energy to another form of energy And it’s measured in watt.

and the symbol for power is the letter (P). Electric power is calculated

with the following equation

. ث اغبص اطبلخ اىشثبئ١خ إ شى آخش أشىبي اطبلخ اؼذي از ٠ؾي :امذسح ااؽ امذسح ل١بط دحػ

.(P) ثبؾشف حمذسي ٠شض

Another common unit of power is the Kilowatt (KW). One kilowatt is

equal to 1,000 W. Kilowatts are use to express high values of power,

such as the power needed to heat a house. The table below shows the

power rating of some appliances you use every day

و١اؽ رغزخذ زؼج١ش ػ ل١ . اؽ 1000و١اؽ اؽذ ٠غب . ؽذح آخش م١بط امذسح و١اؽ

٠ج١ اغذي أدب امذسح جؼغ األعضح از رغزخذب ١٠ب. اطبلخ االصخ زذفئخ اضيػب١خ اطبلخ ، ض

Power = voltage X current or

P = V X I


- 33 -

Table 1

Measuring Electrical Energy

Electric power companies sell electrical energy to homes and

businesses. Such companies determine how much a household or

business has to pay based on power and time. For example the amount

of electrical energy used by a household depends on the power of the

electrical devices in the house and how long those devices are on. The

equation for electrical energy is as follow:

Electrical energy = power X time or

E = P X t

زمنال Xانقذرة = انطاقة

ابصي ب رذفؼ د مذاسرؾذ اىشثبء ششوبد. ابصي اششوبد إث١غ اطبلخ اىشثبئ١خ دششوبد اطبلخ اىشثبئ١خ

عزخذخ لج األعش رؼزذ ػ ػ عج١ اضبي و١خ اطبلخ اىشثبئ١خ ا. ح الذدسػ أعبط اك اششوبد أ

.افزشح اض١خاألعضح اىشثبئ١خ ف اضي دسحق


- 34 -

Measuring Household Energy Use

Households use varying amounts of electrical energy during a day.

Electric companies usually calculate electric energy by multiplying the

power in Kilowatts by the time in hours. The unit of electrical energy is

usually Kilowatt-hours (KWH). If a households used 2,000W (2 KW) of

power for 3 hours, it used 6KWh of energy.

Electric power companies use electric meter such as the one shown in

figure 1 , to determine the number of kilowatt- hours of energy used

by a household. ح ػ ؽش٠ك اطبلخ اىشثبئ رؾغتششوبد اىشثبء . و١بد زفبرخ اطبلخ اىشثبئ١خ خالي ٠ اؽذ األعش رغزخذ

، إرا اعزخذذ األعش عبػخ -و١ اؽ اطبلخ اىشثبئ١خ ل١بطؽذح .عبػبداي ػذد ف ثبى١اد امذسحػشة

. اطبلخ 6KWhعبػبد ، 3 اىشثبء ذح( و١ اؽ 2)اؽ 2000 عبػخ اطبلخ -اؽ و١ايرؾذ٠ذ ػذد ل . 1 ػذاد اىشثبء ج١ ف اشى عزخذدششوبد اطبلخ اىشثبئ١خ

اغزخذخ Figure 1

Calculating the energy used: Sample problem مثال

How much energy is used to dry clothes in a 3KW dryer for 30

minutes? أحسب مقذار انطاقة انمسحخذمة نحجفف انمالبس إرا كانث قذرة

.دققة 30واط واسحخذو انمجفف نمذة كهى 3انمجفف هى

What do you know? Power = 3.0 KW time =0.5 hr

ماذا تعرف؟ كهى واط 3:ساعة انقذرة 0.5: انىقث

What do you want to find out? Energy used انطاقة انمسحخذمة ماذا تريد أن تعرف؟

Write the formula E =Pt

انسمن Xانقذرة = انطاقة : أكتب المعادلة

Substitute into the formula E = 3.0 KW X 0.5 hr

Calculate and simplify E =1.5 KWh


- 35 -

Choose the correct answer أخخش اإلجابت الصحيحت

1-Which of the following is the rate at which electrical energy is

changed into other forms of energy? :ث اغبص اطبلخ اىشثبئ١خ إ شى آخش أشىبي اطبلخ اؼذي از ٠ؾي

a. electric current انحار انكهربائ

b. electric power انقذرة انكهربة

c. voltage انجهذ

d. kilowatt كهى واط

2. In the formula P = V x I, what does the P stand for?

P مارا جعن P = V x I فى انمعادنة

a. performance األداء

b. power انقذرة

c. price انسعر

d. energy انطاقة

2) . Name two common units of power اكخب وحذاث قياس القذسة

_____________________________________________________

___________________________________________________

3)What happens to a light bulb as power increases? ؟عنذما حزداد القذسةما الزي يحذد لضىء لمبت

_____________________________________________________

_____________________________________________________

___________________________________________________

4). One kilowatt is equal_____________ W. واط-----------------------------واحذ كهى واط ساوي


- 36 -

5)Name two ways you can help to save energy.

-:أركر طرقحن نهحفاظ عهى انطاقة

_____________________________________________________

_____________________________________________________

___________________________________________________

6- A hair dryer is plugged into 120 V outlet, it has 9 A current in it .

What is the hair dryer's power rating? لذسح اغفف ب . اج١ش 9مذاس ر١بس ٠ش ف١، فذ 120سق عذ مذاس فةي صغفف اشؼش

_____________________________________________________

_____________________________________________________

_____________________________________________________

___________________________________________________

7- A bulb takes a current of 3A from a 13V battery

a) What is the power of the bulb?

b) How much energy is supplied in 10 seconds? فذ13اج١ش ثطبس٠خ 3ظجبػ ٠ش ف١ ر١بس

ب لذسح اظجبػ؟( أ

_____________________________________________________

_____________________________________________________

_____________________________________________________

___________________________________________________

؟صا 10اىشث١خ ظجبػ ف اؽغت اطبلخ( ة

_____________________________________________________

_____________________________________________________

_____________________________________________________

___________________________________________________

grade 9 unit p.2 electricity & energy electricity and energy · 2010. 12. 28. · grade 9 unit...

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