Electricity and Energy - 1 -
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. 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. Current Alternating Household Generator Dynamo Ampere Key Words اهخ بر يخردد ي زه ي هد د بي ايت ر - 2 -
Introduction: Grade 9 Unit P.2 Electricity & Energy 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. ٠ ى ر ١ ذ ا طبلخ ا ى شثبئ ١ خ ثؼذح ؽشق : ض ا جطبس ٠ بد ؾطبد ر ١ ذ ا ى شثبء ا ز ر فش أغ ت ا طبلخ ا ى شثبئ ١ خ ا غزخذ خ. 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. ػ ذ ر ط ١ ط و شثبئ ثشؾ بد خز فخ ع ف دش ا ىزش بد داخ ا ط. ٠ غ ؽشوخ اإل ىزش بد خالي ط و شثبئ ة اي ر ١ بس ايو شثبئ دؽذد و ١ خ ا ز ١ بس ا ى شثبئ ثؼذد اإل ىزش بد ا ز ر ش خالي ا ط. اهجيبر اهنهرببئي وعب types: Electric Current has two اهجيبر اهيببشر Current: 1- Direct 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. اي ر ١ بس اير رذفك دائ ب ف فظ االرغب ٠ غ ا ز ١ بس ا جبشش. ٠ ج ١ ا شى 1 أد ب األلطبة اي عجخ ا غب جخ ا ط خ ثغ ه إلػبءح ظجبػ و شثبئ. ا ز ١ بس ا جبشش ٠ خشط ا مطت ا غب ت ا جطبس ٠ خ. اهجيبر اهىجردد Current: 2- Alternating 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. ا ز ١ بس ا ز ٠ غ ١ ش ارغب ثظ سح ا جبشش. زظ خ ا ز ١ بس ا ذسدد. ا ز ١ بس ا غزخذ ف ا بصي ا ز ١ بس ا ذسدد ١ ظ - 3 -
Figure 1 لمارا يسخخذم الخياس المخشدد used? Why Alternating Current is 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. األعالن ا ز رؾ ر ١ بسا جبششا دعخ ٠ زظ ؽشاسح. ػ ذ ب رجؼش ؾطبد اي ر ١ ذ ا ى شثبء إ ا غز ى ١ رى و ١ خ ا ؾشاسح ا جؼضخ ا ز ١ بس ا جبشش ػب ١ خ ف رظ ش األعالن, إ ب ا ز ١ بس ا زشدد ٠ زظ ؽشاسح ال ٠ ظجؼ أوضش أ ب ب. زا ا غجت ٠ غزخذ ا ز ١ بس ا زشدد. 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. ثب شغ أ ؼظ األع ضح ا ض ١ خ رغزخذ ر ١ بس زشدد إال أ ثؼغ األع ضح رغزخذ ر ١ بس جبشش زا رؾز ر األع ضح ػ ؾ الد زؾ ٠ ا ز ١ بس اي زشدد إ جبشش. The electric current can be measured by connecting an ammeter across the terminals of the cell. (See Figure 2). )أ ١ زش (. ٠ ج ١ ا شى 2 Figure 2 ا غ بص ا ز ٠ م ١ ظ ا ز ١ بس ا ى شثبئ - 4 -
The SI unit of current is the ampere (A), which is sometimes called (amp). The symbol for current is letter (I). ا ؽذح ا غزخذ ح م ١ بط ا ز ١ بس أ ج ١ ش. س ض ز ١ بس ا ى شثبئ ثب ؾشف (I) Figure 3 جوهيد اهنهرببء 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. ٠ ز ر ١ ذ ؼظ ا طبلخ ا ى شثبئ ١ خ ف ؾطبد ر ١ ذ ايؽبلخ ى إرا و ذ رشوت دساعخ غ د ٠ ب فأ ذ ؾطخ ر ١ ذ ا ى شثبء إ ب ا طبلخ ا خبطخ ةن ا د ي رغؼ ايد ٠ ب ٠ ذ و شثبء شؼ األػ اء. 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. ػ ذ ب دسوت ا ذساطح ايػغ خا خ ف ١ خ رؼسن اي مجغ ف ب ٠ خ ايد ٠ ب ا طبلخ ا ز رؾشن ث ب ا ؼغ خ رزؾ ي إ ؽبلخ و شثبئ ١ خ زا ضبي ػ ذ و شثبئ ثغ ١ ؾ. داخل يحطت جوهيد اهنهرببء Station: Inside a Power Figure 4 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. رؾز ؾطبد ر ١ ذ ا ى شثبء ػ ذاد اوجش ا ذساعخ. ا شى. 5 رذاس ث بء زؾشن ) ؾطخ ؽبلخ و ش بئ ح( ف ر ذ ؽبلخ و شثبئ ١ خ وج سح ثزذ ٠ ش ا ذاد. - 5 -
Figure 5 اهيحرنبث واهيوهداث Generators: Motors and A generator or a dynamo is similar to an electric motor, working in reverse. You can even make a motor work like a generator. 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. ا ذ أ ا ذ ٠ ب شبث ر س و شثبئ ى ٠ ؼ ثب ؼىظ. 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. ا ذ ا ى شثبئ ف ٠ ذ س ف غبي غ بؽ ١ غ. ٠ ؾ ي ا طبلخ ا ؾشو ١ خ إ ؽبلخ و شثبئ ١ خ. ا ر س ا ى شثبئ ف ٠ ذ س ف غبي غ بؽ ١ غ. رؾ ي ا طبلخ ا ى شثبئ ١ خ إ ؽبلخ ؽشو ١ خ. Figure 6-6 -
Inside a Coal-Fired station powered (by steam): يحطت جوهيد اهطبكت )اهبخبر ) ببهفحى Grade 9 Unit P.2 Electricity & Energy 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. ػ ذ ؽشق ا فؾ ا طبلخ ا ؾشاس ٠ خ رؾ ي ا بء ف ا شع إ ثخبس, ا شع ٠ شج غال ٠ خ ػ اللخ ر زظ ثخبس ؽبس عذا. ا جخبس ا ؾبس ٠ ذفغ خالي أ بث ١ ت زذ ٠ ش اي ر سث ١ بد ا ز رذ ٠ ش ا ذ ز ١ ذ ا ى شثبء.. Figure 7-7 -
Fill in the blanks below: 1. The flow of electrons through a conductor is called شر ب االهنخر بح خالل اهي صل شيى 2. Current that change direction at a regular rate is called current اهخ بر اهذي غ ر اخجب تيعدل ي خظى 3- When charges always flow in the same direction, there is a(n) current. ع ديب خخدرم ااهشد بح ف اخجب ادد ش ف ن بم ----------------------------- 4- A battery is a source of current اهتطبر ج يصدر هوخ بر ----------------------------------------------- 5- The type of electricity supplied by electric power plants to our homes is ع اهخ بر اهيشخخدى ف اهي بزل --------------------------------------- 6- A converts kinetic energy into electrical energy --------------- د ل اهطبكج اهدرن ج اه طبكج ن رت ج 7- A converts electrical energy into kinetic energy --------------- د ل اهطبكج ث اهن رت اه طبكج درن ج 8- The SI unit used to measure current is -------------------------------- ددث ك بس اهخ بر 9- The device used to measure electric current is اهج بز اهيشخخدى هل بس اهخ بر اهن رت ------------------------------- 10- The symbol for current is اهريز اهيشخخدى هوخ بر ----------------------- ػشف ا ز ١ بس ا ى شثبئ Current: 1. Define Electric 2. Compare :between an Alternating & Direct current first; then between لبس. Motor an Electric Generator & an Electric - 8 -
ا ز ١ بس ا جبششCurrent Direct ا ز ١ بس ا ذسدد Alternative Current ا ؾشن ا ى شثبئ Electric Motor ا ذ ا ى شثبئ Electric Generator طف ؽش ٠ مزب ز ١ ذ ا ى شثبء electricity. 3. Describe two ways of generating 4. Why is it better and safer to use AC at homes. برا ٠ ؼزجش اعزخذا ا ز ١ بس ا زشدد أفضل أوضش أ ب ب ف ا بصي - 9 -
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. 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. Key Words Potential difference Electromotive force Voltage Volt فشق الجهذ القىةالذافعت الكهشبائيت الجهذ الفىلج - 10 -
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? Cell gives electrons potential energy Electrons return to cell Electrons transfer electrons to bulb Electrons lose potential energy: energy radiated Figure 1 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. ف ا شى ا ػؼ أػال الؽظ أ ا خ ١ خ رذفغ ا ىزش بد. اإل ىزش بد رز بفش غ ثؼؼ ب ا جؼغ ض فبئف ا ض جشن ا ؼغ ؽخ ب ؽبلخ وب خ. ػ ذ رذفك اال ىزش بد ثجؾء ف ا ذائشح فئ ب ر م ايؽبلخ ا خ ١ خ إ ا ظجبػ. ف رشغ ا طبلخ فز ١ خ ا ظجبػ ا غبخ خ. فرق اهجهد )اهجهد( عبر خويت cell: PD (Voltage) across a A cell normally has a voltage marked on it. The higher its voltage, the more energy it gives to the electrons pushed out. و خ ١ خ ب ع ذ ىز ة ػ ١ ب. ثض ٠ بدح ا غ ذ رضداد ؽبلخ اال ىزش بد. The scientific name for voltage is potential difference (PD). االع ا ؼ غ ذ فشق ا غ ذ. - 11 -
Voltage (or PD): is the difference in energy per unit charge as a charge moves between two points in the path of a current. ا غ ذ )فشق ا غ ذ(: ا فشق ف ا طبلخ ى ؽذح شؾ خ ػ ذ ب رزؾشن ا شؼ خ ث ١ مطز ١ ف غبس ا ز ١ بس. (PD) can be measured by connecting voltmeter across the terminals of the cell. ٠ مبط فشق ا غ ذ ثز ط ١ اي ف ز ١ زش ػجش ايخ ١ خ. The SI unit of potential difference is the Volt ا ؽذح ا غزخذ خ فشق ا غ ذ ا ف ذ. Figure 2 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 ا غ ذ ػجش ا خ ١ خ )1 ف ذ( فب ػط ؽبلخ )1 ع ي( ا طبلخ ا ىب خ ى شؾ خ. إرا وب فشق ا غ ذ ػجش ا خ ١ خ )21 ف ذ( عزؼط )21 ع ي( ا طبلخ ا ىب خ ى شؾ خ. ىزا... 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. ا خ ١ خ ر زظ ف سق ا غ ذ ثأػ غز ٠ بر ػ ذ ب رى غ ١ ش زظ خ ثذائشح ال رؼط ر ١ بسا. ب ٠ غ )ا م ح ا ذافؼخ ا ى شة ٠ خ ) خ ١ خ. ػ ذ عش ٠ ب ا ز ١ بس ٠ خفغ فشق ا غ ذ ثغجت إ ذاس ا طبلخ داخ ا خ ١ خ. ػ عج ١ ا ضبي, ثطبس ٠ خ ا غ ١ بسح ىز ة ػ ١ ب )12( ف ذ ف ؽ ١ ا ب ر فش )9( ف ذ ػ ذ رشغ ١ ا ؾشن. - 12 -
فرق اهجهد حول دائرة circuit: PDs around a شبؽ Quick Activity اعزخذا ا ف ز ١ زش voltmeter: Using a Connect cell to two lamps in series as shown in figure 3. و دائشح و شثبئ ١ خ خ ١ خ و شثبئ ١ خ ظجبؽ ١ ط ١ ػ ا ز ا و ب ػؼ ثب شى سل 3 Then connect a voltmeter across each one of the lamps as shown in the figure, and then take the reading. ط ع بص ا ف ز ١ زش ػجش و ظجبػ و ب ػؼ ثب شى عغ لشاءح و ع بص. As with an Ammeter, the Voltmeter must be connected the correct way round (+ to +). )+ نيب اهدبل ف األي خر جة خ ص ل اهف هخي خر تبهطر لج اهصد دج نيب ي ضخ تبهشنل )+ إهى يب كراءث voltmeter? What is the reading on your اهف هخي خر Reconnect the voltmeter (always in parallel, across a component) to find the PD across the other lamp. أعد خ ص ل اهف هخي خر )دائيب عوى اهخ ازي( هخل س فرق اهج د عتر اهيصتبح األخر. Then use your voltmeter to find the PD across the cell. ذى اشخخدى اهف هخي خر )دائيب عوى اهخ ازي( هخل س فرق اهج د عتر اهخو ج اهن رت ج. 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. غ ع ا غ ذ خالي ا ظبث ١ ؼ رغب ا غ ذ ػجش ا خ ١ خ. - 13 -
Figure 3 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. ػ ٠ غبس ا شى الؽظ د رذفك اال ىزش بد ف ا ذائشح خالي ا ضثبؽ ١. ثب زب رفمذ ثؼغ ؽبلز ب ف أ ي ظجبػ ا جبل ف ا ضب و ا طبلخ ا ز ر فش ب اي ثطبس ٠ خ ٠ غزخذ ب ا ضثبؽ ١ رمش ٠ جب إ ب األعالن فال رغز ه ؽبلخ رزوش رمش ٠ جب Like the battery, each bulb has a PD across it. ض ا جطبس ٠ خ ى ظجبػ فشق ع ذ 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 ػ ١ ٠ ا شى الؽظ فظ ا ذائشح غ ا ف ز ١ زش زظال ػجش أعضاء ا ذائشح ا خز فخ. ا مشاءاد ر ػ ١ ؼ ا جذأ ا ز ٠ طجك ف أ دائشح ) غ ع فشق ا غ ذ خالي أعضاء ا ذائشح ا خز فخ = فشق ا غ ذ خالي ا جطبس ٠ خ( 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. - 14 -
ر ط ١ ا خال ٠ ب ػ ا ز ا series: Cell in 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. إل زبط أػ فشق غ ذ ٠ ى ر ط ١ ػذح خال ٠ ب ػ ا ز ا و ب ج ١ ف ا شى 4. ا جطبس ٠ خ رؼ غ ػخ ا خال ٠ ب ح ا زظ. Figure 4 Choose the correct answer اخجر اإلجببت اهصحيحت - 15 -
What is the potential difference between two points in a circuit called? يبذا شي فرق اهج د ت لطخ يلب يج a. resistance خ بر b. current ج د c. voltage شد ج d. charge Which letter is used to represent voltage as a symbol? a. G b. C c. V d. I يب اهدرف اهيشخخدى هوخعت ر ع اهج د What happens to the electric current if the voltage becomes larger? يبذا ددد هوخ بر اهن رت ع د ز بدث فرق اهج د لل اهخ بر decreases. a. The current زداد اهخ بر increases. b. The current ال خغ ر اهخ بر same. c. The current stays the خ كف اهخ بر. flow d. No current will Fill in the blanks: اهفراغبث أيلء A. The scientific name of voltage is & it is defined as االع ا ؼ غ ذ -------- ٠ ؼشف ػ ا ---------------------------- ------------------------------------------------------- B. The SI unit of voltage is. ؽذح ل ١ بط ا غ ذ ---------------------------------- C. To measure voltage a is used. م ١ بط ا غ ذ ٠ غزخذ --------------------------------- D. As voltage increased, the provided energy will ------------. ع ف-----------------------------, ثض ٠ بدح فشق ا غ ذ, فب ا طبلخ - 16 -
Answer the following questions ب ا م ح ا ذافؼخ ا ى شثبئ ١ خ force? 1. What is Electromotive 2. What is the difference between the two circuits in voltage? اؽغت فشق ا غ ذ ف ا ذ ائش ا ى سثبئ ١ خ ا زب ١ خ - 17 -
أنيل اهدائرث أد ب نيب و 3- Complete the circuit below as follow a- The empty circle represent a meter. Add the correct letter to show which type of meter it is b- What does it measures? اهدائرث اهفبرغج خدخ ي عوى ج بز هول بس أضف اهدرف اهذي يذل ذا اهج بز يبذا ل س ---------------------------------------------------- c- Add a second meter to the circuit to show how you would measure the voltage across the lamp أضف ج بز خر هل بس فرق اهج د ت طرف اهيصتبح d- What would you expect the reading on this meter to be? يب خ كعم هلراءث اهج بز ------------------------------------------------------------------ ------------------------------------------------------------------ ----------------------------------------------------------------- - 18 -
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. 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. Resistance Key Words اهيلبويت Ohm Omega أوى أوييغب - 19 -
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. ػ د ب ٠ زذفك ا ز ١ بس ا ى شثبئ خالي ع ه و شثبئ فئ اإل ىزش بد رزجبؽأ ل ١ ال ثغجت ا غ ه ا ز ٠ مب اال ىزش بد. RESISTANCE: is the opposition to the flow of electric charge (current). ا مب خ ب غح رذفك اإل ىزش بد )ا ز ١ بس ا ى شثبئ (. Resistance is measured in Ohms and is represented by a Ω, the Greek letter omega. رمبط ا مب خ ثبعزخذا ؽذح أ ا ز ٠ ش ض ة ا ؾشف Ω )ا ؾشف ا الر ١ أ ١ غب(. 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. ٠ ى اػزجبس ا مب خ اؽزىبوب و شثبئ ١ ب. و ب صادد مب خ ا بدح و ب ل ا ز ١ بس ا ى شثبئ ا بس ف ا غ ه ػ ذ صج د فشق ا غ ذ. An object s resistance depends on: اهيلبويت جعجيد عوى وعيت اهيبدة Material: -1 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. ا طالد ا غ ١ ذح ض ا ؾبط ذ ٠ ب مب خ أل. ا طالد غ ١ ش ا غ ١ ذح ض ا ؾذ ٠ ذ ذ ٠ ب مب خ أػ. رغزخذ ا اد راد مب خ ل ١ خ ؼ األعالن غ ١ ش ب األش ١ بء ا ز رغزخذ م ا طبلخ ا ى شثبئ ١ خ ىب إ آخش. Figure 1-20 -
اهسيم 2- Thickness Grade 9 Unit P.2 Electricity & Energy 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 رؼز ذ ا مب خ ػ ع ه ا ط. فب ط ا شف ١ غ أوضش مب خ ا ط ا غ ١ ه. اهطول 3-Length: ا ط ا ط ٠ ذ ٠ مب خ أوضش ا مظ ١ ش Ohm s Law: electric current is directly proportional to voltage and inversely proportional to resistance. ا ز ١ بس ا ى شثبئ ٠ ز بعت ر بعت ؽشد غ فشق ا غ ذ ٠ ز بعت ر بعت ػىغ غ ا مب خ 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. ا ؼب ع سط ا ػؼ ا ؼاللخ ث ١ ا ز ١ بس فشق ا غ ذ ا مب خ ثب ؼبد خ ا ٢ ر ١ خ : Figure 2 Resistance (R) = PD across the wire (V) Current through the wire (I) Ohm (Ω) = Volt (v) Ampere (A) ** 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). ا شى ٠ ج ١ 3 ا ؼاللخ ث ١ فشق ا غ ذ ا ز ١ بس ا ى شثبئ بدح )ثضجبد ا مب خ (. - 21 -
Figure 3 ػشف ا مب خ resistance: 1. Define :. 2. Fill in the blanks below: A. In an electric circuit; the flow of electrons are slowing down because of ف دائشح و شث ١ خ: ٠ ؾذس رجبؽأ غش ٠ ب اال ىزش بد ثغجت. B. If the voltage is constant ; decreasing the resistance, will---------- the current ػ ذ صجبد فشق ا غ ذ رم ١ ا م خ ع ف----------------- ا ز ١ بس C. Resistance is measured in ثبعزخذا ؽذح -------------------------------------- رمبط ا مب خ D. The higher the resistance of a material is, the lower the كهما رادت مقاومة انسهك, كهما قم ----------------------------------- E. Good conductors have a(n) resistance ا طالد ا غ ١ ذح رى مب ز ب ----------------------------------------- - 22 -
أذنر ا ؼ ا ا ز رؤصش ػ ا مب خ resistance. 3. Describe the factors that affect ----------------------------------------------------------------------------------- ----------------------------------------------------------------------------------- -----------------------------------------------------------------------------------. 4. Why are high resistance materials useful in light bulbs? برا رغزخذ ا اد راد ا مب خ ا ؼب ١ خ ف ط بػخ ا ظبث ١ ؼ ----------------------------------------------------------------------------------- ----------------------------------------------------------------------------------- ---------------------------------------------------------------------- 5. Explain, step by step, how to calculate the amount of current (I) that will go through the resistor in this circuit below. اششػ خط ح ثخط ح و ١ ف ٠ ز ؽغبة ا ز ١ بس ا ى شثبئ خالي ا مب ف ا شى ا زب - 23 -
6. What is the value of this resistor, in Ohms )Ω(? ب ل ١ خ ا مب ح )اعزخذ ا ( 7-A resistor has a steady resistance of 8 Ω : مقاوو نه مب خ لذس ب 8 Ω a- If the current through the resistor is (2A), what is the PD across it? ب مذاس فشق ا غ ذ إرا وب ا ز ١ بس ٠ غب,(2A) ---------------------------------------------------------------------------------------------------------------- - b- If the PD falls to (6V), what is the current? إرا وب فشق ا غ ذ,(6V) ف ب ل ١ خ ا ز ١ بس --------------------------------------------------------------------------------------------------------------- 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 األعالن ا ػؾخ ظ ػخ ا ؾبط ب فظ دسعخ ا ؾشاسح. أ ٠ ب مب خ أل غ روش ا غجت ------------------------------------------------------------------------------------------ -------------------------------------------------------------------------------------- 8- Search : use the internet to find out What are superconductors? - 24 -
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. 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. Fuses Ring main Key Words المنصهش الذائشة الشئيسيت - 25 -
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). ٠ ز ر ١ ذ ا طبلخ ا ى شث ١ خ ف ؾطبد ر ١ ذ ا طبلخ ا ز ر زظ ر ١ بسا زشددا " ص رشع ا طبلخ خالي وبثالد ؽ ٠ خ ا غبفخ ص ر صع ػ ا غز ى ١. ػ ذ ر ط ١ غال ٠ خ )أ غ ١ ش ب األع ضح( ف ا مجظ ا شئ ١ غ ٠ ز ر ط ١ إ دائشح و شثبئ ١ خ. إ ذاد ا ز ١ بس ا ى شثبئ )V ) 230 مبثظ ا شئ ١ غ ١ خ ايد ائش ا ض ١ خ األخش. ا ز ١ بس ا شئ ١ غ ا ز ١ بس ا ذسدد ا ز ٠ زذفك إ ا خ ف األ ب 50 شح ف ا ضب ١ خ ا اؽذح ػ ذ ب ٠ ى اي رشدد ا شئ ١ غ 50 شرض. - 26 -
اا Household Wiring: Here is a simplified diagram of a modern household circuit. It is in two parts: A. The lighting circuit. B. Ring main. ا ؾذ ٠ ضخ. عضئ ١ : ا شى أد ب ٠ ػؼ سع رخط ١ ط جغؾ يذ ائش ا ض ١ خ ا ذائشح ح ا شئ ١ غ. - د سح اإلػبءح. - 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 أعالن ؽ ١ خ ا مبد خ ؾطخ ر ١ ذ ا ى شثبء )خطشح ا زؼشع لذ ٠ مز (. = N األعالن ا رؼبد خ ا مبد خ ؾطخ ر ١ ذ ا ى شثبء = E ايع ه ا ط ثبألسع غال خ إرا ش ف ١ ر ١ بس و شثبئ ف ١ ى ثب خطأ ٠ ز ة اي ظ ش. The 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. ششوبد ا ى شثبء,ر ط أعالن ؽ ١ خ زؼبد خ إ ا غز ه. ف ؽذح ا غز ه ر ط ا طالد ثذ ائش ر ط ١ ػ ر اص إلػبءح ا مبثظ ا شئ ١ ظح. Diagram 1-27 -
ا ذائشح ا شئ ١ غ ١ خ رؼش ف as: Ring Main defined 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. ا ىبث ا ز ٠ جذأ ٠ ز ف ؽذح ا غز ى ١ غ األعالن ايؽ ١ خ يا رؼبد خ األسػ ا ز رشى ؽ مخ ؽ ٠ خ ف ع ١ غ أ ؾبء ا ضي ٠ ز ر ط ١ لبثظ ا ز ١ بس ا ى شثبئ إ ا ذائشح ح ا شئ ١ غ و ب ػؼ ف ا شع اي رخط ١ ط. 1 أجهزة السالمت Devices: Safety المنصهش Fuse: 1- 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. ع ه لظذ ٠ ش سل ١ ك ٠ ز اعذ ف ايد ائش, طالد ػؼ ١ فخ ػغد غال خ ر ه ثز ثب ػ ذ ش س ر ١ بس و شثبئ ػب ثب خطأ ف ١ غ ؽذ س أػشاس أ ؽش ٠ ك. قاطع الذائشة Breaker: 2- Circuit Diagram 2 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. ٠ غبػذ ف عؼ ا ى شثبء أوضش أ ب ب, ٠ مطغ ا ز ١ بس ا ى شثبئ أ ر بر ١ ى ١ ب ػ ذ ب ٠ ش ر ١ بس ػب. السلك األسضي Wire: 3- Earth 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. إرا ؽظ خطأ ف األعالن ا ؾ ١ خ ال ظ ا ظ ذ ق ا ؼذ, ع ١ ش ر ١ بس و شثبئ ػب ا غ ه ا ؾ ا ع ه األسع ف ١ مطغ اي ظ ش. زا ٠ غؼ ا غ بص غ ١ ش أ ؾ ١ رغ ١١ ش اي ظ ش. - 28 -
Do You Know Many appliances have an earth connection. This is particularly important for appliances with metal cases, including heaters and washing machines. - 29 -
Look at the diagram to the right. Explain what ػؼ برا is :L, N & E. أ ظش ا ا شع ص E & N & L ع ى ---------------------------- ---------------------------- ---------------------------- ---------------------------- ---------------------------- ---------------------------- ---------------------------- ---------------------------- ----------------------------. ب ا ظ ش work? What is fuse? How does it و ١ ف ٠ ؼ -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -----------------------------------------------------------------------------. ب اي فشق ث ١ ا ظ ش لبؽغ ا ذائشح. fuses? How do circuit breakers differ from -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -----------------------------------------------------------------------------. ب أ ١ خ ا غ ه األسػ important? Why is the Earth wire -------------------------------------------------------------------------------- ------------------------------------------------------------------------------. - 30 -
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. Power Watt Rate Appliances Convert Key Words انقذرة واط معذل أجهسة يحىل - 31 -
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). ٠ ز اعزخذا ا طبلخ ا ى شثبئ ١ خ م ١ ب ثأػ بي ف ١ ذح بطرق ػذح ف األع ضح ض ا مذ س ا ؾب ض خالؽبد رؾ ي ا طبلخ ا ى شثبئ ١ خ )رغ ١١ ش ا إ أشىبي أخش (. ػ عج ١ ا ضبي أع ضح اي رغخ ١ دؽ ي ا طبلخ ا ى شثبئ ١ خ إ ا طبلخ ا ؾشاس ٠ خ )ا ؾشاسح (. 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 يا Power = voltage X current or P = V X I ا مذسح: ػدح ٠ ش ض ا ؼذي ا ز ٠ ؾ ي ث ا غ بص ا طبلخ ا ى شثبئ ١ خ إ شى آخش أشىبي ا طبلخ. ل ١ بط ا مذسح ا اؽ ي مذسح ثب ؾشف.(P) 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 ؽذح آخش م ١ بط ا مذسح و ١ اؽ. و ١ اؽ اؽذ ٠ غب 1000 اؽ. و ١ اؽ رغزخذ زؼج ١ ش ػ ل ١ ػب ١ خ ا طبلخ ض ا طبلخ ا الص خ زذفئخ ا ضي. ٠ ج ١ ا غذ ي أد ب ا مذسح جؼغ األع ضح ا ز رغزخذ ب ١ ٠ ب - 32 -
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 انطاقة = انقذرة Xال زمن ششوبد ا طبلخ ا ى شثبئ ١ خ د ث ١ غ ا طبلخ ا ى شثبئ ١ خ إ ا بصي ا ششوبد. ششوبد ا ى شثبء رؾذد مذاس ب رذفؼ ا بصي أ ا ششوبد ػ أعبط ا كدسح ا لذ. ػ عج ١ ا ضبي و ١ خ ا طبلخ ا ى شثبئ ١ خ ا عزخذ خ لج األعش رؼز ذ ػ قدسح األع ضح ا ى شثبئ ١ خ ف ا ضي ا فزشح ا ض ١ خ. - 33 -
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. األعش رغزخذ و ١ بد زفب رخ ا طبلخ ا ى شثبئ ١ خ خالي ٠ اؽذ. ششوبد ا ى شثبء رؾغت ا طبلخ ح ا ى شثبئ ػ ؽش ٠ ك ػشة ا مذسح ثب ى ١ اد ف ػذد ايعبػبد. ؽذح ل ١ بط ا طبلخ ا ى شثبئ ١ خ و ١ اؽ - عبػخ إرا اعزخذ ذ األعش 2000 اؽ )2 و ١ اؽ( ا ى شثبء ذح 3 عبػبد KWh6 ا طبلخ. ششوبد ا طبلخ ا ى شثبئ ١ خ دعزخذ ػذاد ا ى شثبء ج ١ ف ا شى. 1 لرؾذ ٠ ذ ػذد ايو ١ اؽ - عبػخ ا طبلخ ا غزخذ خ Figure 1 مثال Calculating the energy used: Sample problem How much energy is used to dry clothes in a 3KW dryer for 30 أحسب مقذار انطاقة انمسحخذمة نحجف ف انمالبس إرا كانث قذرة minutes? انمجفف هى 3 ك هى واط واسحخذو انمجفف نمذة 30 دق قة. What do you know? Power = 3.0 KW time =0.5 hr ماذا تعرف انقذرة: 3 ك هى واط انىقث: 0.5 ساعة What do you want to find out? Energy used ماذا تريد أن تعرف انطاقة انمسحخذمة Write the formula E =Pt Xانسمن انطاقة = انقذرة أكتب المعادلة: Substitute into the formula E = 3.0 KW X 0.5 hr Calculate and simplify E =1.5 KWh - 34 -
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? ا ؼذي ا ز ٠ ؾ ي ث ا غ بص ا طبلخ ا ى شثبئ ١ خ إ شى آخش أشىبي ا طبلخ : انح ار انكهربائcurrent.a electric انقذرة انكهرب ة b. electric power انجهذ c. voltage ك هى واط.d kilowatt 2. In the formula P = V x I, what does the P stand for? فى انمعادنةI P = V x مارا جعنP األداء a. performance انقذرة b. power انسعر c. price انطاقة d. energy اكخب وحذاث قياس القذسة. Name two common units of power 2) 3)What happens to a light bulb as power increases? ما الزي يحذد لضىء لمبت عنذما حزداد القذسة 4). One kilowatt is equal W. واحذ ك هى واط ساوي ----------------------------- واط - 35 -
5)Name two ways you can help to save energy. أركر طر قح ن 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? غفف ا شؼش صي ةف سق ع ذ مذاس 120 ف ذ ٠ ش ف ١ ر ١ بس مذاس 9 ا ج ١ ش. ب لذسح ا غفف 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? ظجبػ ٠ ش ف ١ ر ١ بس 3 ا ج ١ ش ثطبس ٠ خ 13 ف ذ أ( ب لذسح ا ظجبػ ة( اؽغت ا طبلخ ا ى شث ١ خ ظجبػ ف 10 ص ا - 36 -