Sciences Subject (BS 21001)

251 5. Friction force is the force exerted by surfaces of objects consisting of 2 types; Static friction is friction between two or more solid objects that are not moving relative to each other. Kinetic friction occurs when two objects are moving relative to each other and rub together. Friction Force Friction force is the force resisting the relative motion of an object, whenever the surfaces of the objects move across another surface. The friction also occurs as the attempted motion of the objects or the moving objects against another object relative to the force. The important characteristics of friction are 1. Occur between the surfaces of the objects 2. Act opposite to the direction of the object or the attempted motion of the object as the figure shown below; Figure shows the characteristic of friction If you place Object A on B, then apply the force to move Object A, whether moving or not, the friction will occur between the surface of Object A and B. The friction act opposite to the direction of the force attemptively resisting the motion of Object A.

252 Types of friction force Friction force composes of 2 types that are 1. Static friction is friction between two objects that are not moving relative to each other. 2. Kinetic friction occurs when two objects are moving relative to each other with the contant velocity. Factors affecting friction The amount of friction between two surfaces depends on 1. The compressive force vertical to the surface: The more the compressive force is vertically applied, the more friction is. On the contrary, if the compressive force contacting the surface is little, the less friction will occur. As firgure shown below; Figure A is low friction. Figure B is high friction. 2. The surface characteristics of materials If the contacting surface is rough, it will experience more friction as Figure A, on the other hand, if the surface is smoother, there is less friction as Figure B. Figure A is high friction Figure B is low friction

253 3. Types of the contacting surfaces such as concrete with a iron bar, and a iron bar with wood. Each of their surfaces has the different smoothness resulting to the unequal friction. Reducing Friction There are several ways to reduce friction by using 1. Lubricants or oil 2. Roller bearing systems 3. Devices such as taped roller bearings 4. Streamlining transportation designs to reduce friction Increasing Friction There are many ways to increase friction for safety such as 1. Provide grip for vehicle tires to increase the friction force between the tires and roads. 2. Increase the friction at the brakes in order to stop or slow down the cars. 3. Design the soles of the shoes to prevent from falling over when walking. 4. Lay the rough tiles in the bathroom relative to the slip resistance. The properties of friction 1. The force of friction is values zero as there are no forces applied upon the objects. 2. While there is applied force acting on an object, remaining, the coefficient of friction has a different amount depending on the applied forces. At that time, the coefficient of static friction, occurring when the objects start moving, reaches the most value. 3. The friction exerts a force opposite to the direction in which an object is moving. 4. The coefficient of static friction is a little larger than the coefficient of kinetic friction. 5. The force of friction depends on the characteristics of contacting surfaces; the rough surfaces create more friction than the smooth ones. 6. The force of friction is dependent upon weight or the amount of contact force pushing on the ground. If the compressive force is doubled, the force of friction becomes doubled.

254 7. The friction does not depend on the surface area. The advantages of friction 1. The advantages of increasing friction; - Knots and screws have a nut to increase the friction resulting in the more interactive force. - Design of tire tread helps the tires to grip the roads relative to the slip resistance. - Tread patterns of the shoe soles are designed to be rough in order to increase friction between the ground and the shoe soles for having a balanced stride. 2. The advantages of decreasing friction - Help to reduce the friction in human joints while they are in motion such as the lubrication of brain and spinal cord. - Use lubricants or motor oil between the two surfaces to reduce the friction. - Use polytetrafluoroethylene (PTFE), the trade name is Teflon, to coat on the bearing without lubricating. Lesson 2 Moments Moment is the tendency of a force to rotate an object about fulcrum The value of the moment is calculated from the product of force interacting with the square of its distance from the axis of rotation as the formula of M = F x S or

255 There are 2 directions of the moment; 1. Clockwise moment The seesaw AB has the fulcrum of F. Apply the force to the tip of A, then the seesaw will turn in a clockwise direction called a clockwise moment. 2. Anticlockwise moment The seesaw AB has the fulcrum of F. Apply the force to the tip of B, then the seesaw will turn in an anti clockwise direction called an anticlockwise moment. Figure shows the direction of the moment According the figure shown, F is the fulcrum. Place an object to the right hand side, then push the other end of the seesaw to stay level. Clockwise moment = W x L2 (Newton/meter) Anticlockwise moment = E x L1 (Newton/ meter) The principle of moments

256 When the forces are applied to an object, and the object is in the state of equilibrium (stay level and not rotate) stating that The total sum of the clockwise moment = the total sum of the anticlockwise moment Lever The principles of moments are applied to the instrument called lever. The lever is one of mechanical devices used in raising or moving an object to be pivoted about fulcrum. In addition, the lever is a long rigid piece of metal or wood. The lever is used by applying the principles of moments. Figure shows the lever characteristic. If the weight of lever is not stated, it means that the lever has no weight. According to the figure; W = Resistant force or the weight of an object (the load) E = Applied force (Effort) or the force acting the lever a = The distance squaring from the fulcrum to the point where the resistant force is applied. b = The distance squaring from the fulcrum to the point where the motive force is applied. Additionally, F is the pivot point or the fulcrum

257 When the lever is in the state of equilibrium: The clockwise moment = The anticlockwise moment Wxa=Exb The levers are classified to 3 classes as follows; 1. A first-class lever has the fulcrum (F) located between the applied force (E) and the resistant force (W) such as scissors, nail clippers, pliers, paddling boats, and see-saws etc. Figure shows a first-class lever 2. A second-class lever has a resistant force between the effort (E) and the fulcrum (F), for instance, can openers, wheelbarrows, paper cutters etc. Figure shows a second-class lever

258 3. A third-class lever has the effort (E) placed between the resistant force (W) and the fulcrum (F) such as chopsticks, coal tongs, tweezers etc. Figure shows a third-class lever The labor-saving of labor depends upon the relative positions of E, F and W. If the distance of EF is longer than the distance of WF, it will save labor. Alternatively, if the distance of EF is shorter than the distance of WF, it won’t save labor. The principles and procedures for calculating the moments and levers 1. Draw a picture of lever and determine the location of all forces acting on the lever. 2. Locate the position of the pivot or the fulcrum. If it is not stated, assume it. 3. If the weight of lever is not stated, it is considered that the lever stays level. 4. If the weight of lever is stated, it is also included in the calculation regarding the weight is always in the middle of levers. 5. When a lever is in the state of equilibrium, the clockwise moment is equal the anticlockwise moment. 6. Either the clockwise or anticlockwise moment has the value which is equal the total sum of each type of individual moment.

259 The examples of the calculation of moments Example 1 A lever is light-weight. There is a load of 300 Newton (N) which hang in the end of lever and is 1 meter from the fulcrum. What location on the other side of the lever is required to hang a load of 150 N to balance the lever? Solution It is supposed that the load of 150 N hangs in x meter from the fulcrum; F = x meter (the moment is at F) 1. Draw a diagram showing all forces acting on the lever. A B 1 X 150 N 2. Determine F as the fulcrum. Calculate the value of the clockwise and anti clockwise moments. The clockwise moment = 150 x (X) = 150X Nm The anticlockwise moment = 1 x (300) = 300 Nm 3. According to the principles of moments The clockwise moment = the anticlockwise moment 150X = 300 X = 300/150 = 2 m Answer The load of 150 N is 2 meters from the fulcrum.

260 Example 2 A lever is 6 m long, has a mass of 150 N lifting a rock which has a load of 3000 N and is 1 m from the fulcrum. How much weight do you need to push on the other end of the lever to lift the rock? F A 1N 2 B 3 200 N Solution It is supposed that the force is applied at B = X N and the moment is at F The clockwise moment = the anticlockwise moment (X x 5) + (200 x 2) = 1 x 3000 5X + 400 = 3000 5X = 3000 – 400 = 2600 X = 2600/5 = 520 Answer The effort is 520 N. Example 3 A see-saw is 5 m long. Mr. A has a weight of 400 N standing at the end of A. Mr. B has a weight of 600 N standing at the end of B. What position is the fulcrum located to balance the lever? Solution It is supposed that Mr. A is X m from the fulcrum. The clockwise moment = the anticlockwise moment 600 (5 – X) = 400 x X 6 (5 –X) = 4X 30 – 6X = 4X 30 = 4X + 6X 30 = 10X X = 30/10 = 3 Answer Mr. A is 3 m from the fulcrum.

261 The use of moment in every day life The knowledge of the moments can be applied in every day life, for instance, to play on see-saws, to use shoulder poles, Chinese scales, to hang mobiles, can openers, wheelbarrows, pliers, and paper cutters etc. Moreover, use ropes or sling in order to hold the lever out of the walls. Exercise 1. Answer the questions below 1.1 What is the meaning of force? 1.2 What are the results of the applied forces? 1.3 What is the unit of force? 1.4 What is friction? 1.5 Why do present transporters have wheels? 1.6 Why do cars have tapered roller bearing, wheels? and why do they need to lubricate? 1.7 What factors does the coefficient of friction depend on? 1.8 A tennis player hit a ball so hard. While the ball is in the air, what forces are acting on the ball? 1.9 If you weigh yourself near a table and push the table while you are weighing, will the value reading from the weight scale increase or decrease? And why? 1.10 What are moments? How many types of them? 2. The lever is 3 m long used to lift an object which has a load of 400 N. The object is 0.5 m from the fulcrum. Calculate how much force is required to place at the other end to balance the lever? (Show a solution)

262 Lesson 12 Work and Energy Essence Study the definition of work and energies, types of energies, electric energy, Ohm’s law, the connection of all resistive circuits, calculating the values of resistance, the advantages of electricity in daily life and the electrical energy conservation, light and its properties, types of lenses, the advantages and disadvantages of light to life, the sources of heat energy, the beneficial uses of heat, and alternative energies. Expectation Learning Outcomes 1. Explain the meaning of work and energies. 2. Connect a simple electric circuit. 3. Use the Ohm’s law calculations. 4. Determine the methods of energy conservation and energy efficiency. 5. Explain the properties of light and heat energy and the beneficial uses in every day life. 6. Explain the alternative energies. Scope of Content Lesson 1 the definition of work and energies Lesson 2 types of energies Lesson 3 electricity Lesson 4 light

263 Topic 1 Definition of work and energy 1.1 WORK There are varieties of meaning for the word ‚work‛, such as: Have you work yet? Is there a lot of work? Let’s do housework. Though in science these kind of work is not really work. In science work is when a force acts to move an object in the direction that the force was done on the object, which are shown in the picture: People lift an object from the Several people are pushing the ground onto the truck. mired vehicle. Work in our daily life W=FxS …………………… (1) We specified that W is the work that is calculated into unit called joule or Newton - metre (N.m) F is the force done on an object with unit called Newton : N S is the distance that the object move in the direction where the force is done on the object with the unit Meter : m 1.2 ENERGY In our daily life we always hear the word energy for example we get energy from food. There are different kinds of source of energy that can make our world to work and if you

264 do an in-dept analysis you will find that most of source of energy that we use in our daily life come from the enormous energy radiating from the sun to the earth. We call this form of energy solar energy. We can directly utilized solar energy from the rays and the heat for example to give light, heat to keep warm, dry our clothes or things and create many other energy sources such as:  Wind energy in the form of Kinetic energy  Water energy in the form of Potential energy of rainfalls and are stored in high place  Ocean energy in the form of kinetic energy of waves, tides and thermal energy in the water of the ocean.  Biomass energy in the form of chemical energy of biomass.  Fossil fuel in the form of chemical energy of coal, oil and natural gas. In other words, this implies that these energy sources are another indirect energy sources of the Sun.

265 Topic 2 Different Form of Energy Energy that we use comes in different forms such as we use chemical energy from nutrients in our body that carries different substances throughout the body. In moving those substances we called mechanical energy. We use heat energy in cooking and keeping warm as well as making steam engine, which all of these create mechanical energy. Light energy helps us see things around. We can hear and use electric energy with electric appliances. Form of energy can be categorized in to 2 groups, active energy and stored energy.  Stored energy such as chemical energy, potential energy and nuclear energy  Active energy is energy that occurred from activities such as heat energy, light energy, sound energy and kinetic energy.  Other form of energy such as biomass energy. Energy that is stored Energy that is stored in the matters:  Chemical Energy  Nuclear Energy  Potential Energy Potential Energy Potential energy is stored energy of position possessed by an object within a force field. There are 2 forms of potential energy, gravitational potential energy and elastic potential energy. Gravitational Potential Energy Gravitational potential energy is the energy stored in an object as the result of its vertical position or height. The energy is stored as the result of the gravitational attraction of the Earth for the object. Potential energy that is in high position occurs from the gravity of earth done on the objects. If we lift mass objects (m) up vertically from the ground (h) and the object is moving at a constant speed, we will have to exert (F) at the amount equal to the mass of the object (mg) we then can lift the object as we want. We can get gravitational potential energy from this equation EP = mgh…. (2)

266 Elastic Potential Energy Elastic potential energy is energy stored in the spring or elastic materials when stretching from the equilibrium position. In pulling the spring with the distance x work occurred and the amount of work used to pull the spring creates elastic potential energy. If we replace with elastic potential energy the results will be according to this equation. Ep = ½ kx2 …………………… (3) When K is the value of constant spring Example of calculation: 4 people are sitting in a car, 2 sit in front and 2 sit at the back. Each individual has a mass of 80 kilograms. The spring of the shock absorbers are press down with the distance of 3 centimeters. What is the value of constant spring and elastic potential energy of each spring? How to find constant value of spring From F = kx and F = ma Mg = mk k = mg x k = (80x4)9.8 0.03 k = 10.45x104 N:m

267 Find gravitational potential energy EP = ½ kx2 Ep = ½ (10.45 x 104) x (0.030)2 = 47.04 joules Nuclear Energy Fore nuclear reaction to occurs we need uranium and deuterium as a fuel, which can be considered that these energy sources originate from our earth. Albert Einstein, a well-known scientist, the first person who invented physic equations that mass can be converted to energy (E) and energy that occurs has equal amount (m) with the missing reaction times light speed (c) squared 2 E = mc2 …………………… (4) It is commonly know that light travel fast (3 x 108 meters per second) and when it is squared we get enormous amount of heat and light. There are 2 types of nuclear reactions, Fission and Fusion. Chemical Energy Chemical energy is energy stored in the bond of chemical compounds such as food and fuel. Chemical energy can transform into other form of energy such as food we take into our body and transform into chemical energy then transform into other energy that can be use with different organs in our body. Energy that can work is the energy that occurs from doing activities which comes in many forms  Heat energy  Light energy  Sound energy

268  Electronics energy  Kinetic energy Heat Energy Heat energy that comes from burning of the heat energy stove can be felt. The largest heat energy is the sun. Sound energy Sound energy is a form of energy that occurs from vibrations. Hearing is another form of energy that is very significant in human because we use sound to communicate. Even animal or some plants use sound to send signal to each other, such as sound energy that we get from speaking to each other, sound energy that comes from music instrument and etc. Light Energy Light bulbs give light energy to us. Sun is another source of light energy allowing us to see things, if there is no light energy we will be living in the dark. Electronic energy Energy that makes computers work, can be consume in the large amount and can be use continuously. Kinetic Energy All objects that can move cause by kinetic energy. Objects that move fast means they have a lot of kinetic energy such as driving a car really fast. Finding the kinetic energy of ski player can be done through this equation. If he move with the speed (v) and with mass (m) Ek = ½ mv2 …………………… (5) Example: A car move with a speed of 72 kilometers/ hour, if accelerate to be at the speed of 72 km/hour. How much kinetic energy change does this car move with.

269 Answer = from the equation Ek = ½ mv2 Kinetic energy before change Ek = ½ mv(1,500)(20) Kinetic energy after work change = 3 x 105 joules Ek = ½ mv(1,500)(30) = 6.75 x 105 joules Therefore kinetic energy that changes equal kinetic energy after changes. Kinetic energy before changes = 6.75 x 105 - 3 x 105 joules = 3.75 x 105 joules Answer : Kinetic energy that changes is 3.75 x 105 joules Other Form of Energy There are many sources of energy that can make our world work and if we do an in-dept analysis we will find that most of the energy we use in our daily life originate from the tremendous energy that radiate from the sun to our earth. Energy from this sun can be utilized in many ways such as giving light, giving heat to keep us warm, dry things such as clothes or food and it also creates other sources of energy.  Wind Energy in the form of kinetic energy of the wind  Water Energy in the form of potential energy of rainfall and stored in the high place.  Ocean energy in the form of kinetic energy of waves or tides and heat energy in the ocean water.  Biomass energy in the form of chemical energy of biomass.  Fossil fuel in the form of chemical energy of coal, oil and natural gas. In other words, these energy sources are another indirect energy from the sun.

270 Tidal current Energy Tidal energy that occurred in the sea is categorized separately from other ocean energy that was mentioned earlier because ocean energy occurs from the gravitational pull of the moon more than the sun and it is the only source of energy caused by the Moon that influent our world. The phenomenon of tidal currents occurs when the sun, earth and moon orbit into the same line. Gravity from the sun, which is closer to the earth, pulls water along the equator in the ocean to rises and when the moon is perpendicular to the sun it causes water in the equator area to recede. Tidal cycle of water in the ocean conform with the orbit period of the moon around the earth, which can be observed that water will rise when it is near Lunar phase day base on the lunar calendar. The differences of seawater during high tides and during low tides can be considered as potential energy that can be utilized. Wind energy The major cause of wind energy comes from the heat of the sun ray radiating to our earth causing the air to be unequal. This makes hot air that is less dense to rise and replace by cold air which have more dense such as air near the equator is hotter than air near the pole which is heavier. Lighter air will rise up and replace by heavier air. Wind is natural phenomenon, which derives from the differences of temperature. Pressure of atmosphere and force of the earth’s rotation are the cause of wind speed and strength. It is commonly known that wind is another form of energy within itself, which sometimes the force that occurred from wind may cause houses to collapse, trees to fall down, objects falling down or floating with the wind and etc. Nowadays, human focuses more in utilizing energy from the wind as wind energy is everywhere, it’s free and it is clean energy. Wind energy is environmental friendly and can be utilize continuously.

271 Ocean energy - Wave energy derives from water on the surface of the ocean, which was blown by the wind creating motion called wave. - Tidal current energy has the same characteristic of wind energy. The difference is that instead of air it is water in the ocean. - Heat energy in the sea occurs when the surface of the water in the sea received heat from the sun (at approximately 20 degree Celsius), which is hotter than deep water (at the depths of 1 km, water have the temperature of about 4 degree Celsius). The different of the temperature is another sources of energy. Fossil Fuel Fossil fuel occurs from decomposed of living things under a suitable environment and when the remains of ancient plants and animals (Dinosaur era), buried into layers and layers deep inside the Earth for millions of years. Over a long, long time, heat and pressure has turned these remains into fossil fuel that we call coal, oil and natural gas. The only way to use fossil fuel is to burn them. When fossil fuel is burnt carbon and hydrogen stored inside the fossil fuels combined with oxygen in the air and turned into carbon dioxide. Water as well as other substances, which are the elements of living things that were mixed in the fossil fuel such as sulphur and nitrogen are also released. Reaction of these substances with oxygen in the air released sulphur oxide (SOX) and Nitrogen oxide (NOX) Electric energy Electric energy is important energy and human utilized it the most. Since Thomas Alva Edison successfully invented light bulb in 1879, technologies of electrical appliances have developed rapidly which can be seen around us today. These appliances transform electric energy into other form of energy. Electric current carries electric energy from the power source to the household appliances and industrial plants. We send electric current to places through electric wires that are made from material that allow electric current to flow through.

272 Biomass energy All plants on our earth utilized energy from the sun. Plants transformed solar energy and stored these energy to survive and these energy are the significant substances that help each part of plants grow such as roots, trunks, leaves, flowers, fruits. This significant process on storing solar energy is called photosynthesis. By using chlorophyll on green plants that acts as a small factory, taking carbon dioxide from the air and water from the soil reacting with each chemical producing a group of compound such as sugar, starch, cellulose which if combine together we called carbohydrate. This solar energy is stored in a form of chemical bonds. There are both herbivore and carnivore in animals, human eat both plant and meat for food. This cycle is called food cycle of living things. The cycle allow plants to transfer energy to other animals or living things which can be summarized that all living things work by using energy from the sun and the growth of living things are sources of stored energy received from the sun Biomass energy is energy stored in living things that can be put to work such as trees, branches or scrap from agriculture or industry such as husk, straw, bagasse, saw dust, wood chips, bark, livestock manure including remnant or waste from human household. We have been using energy from biomass for decades and we still uses it especially in development countries like our country, in the rural area still uses firewood or coal to cook food. Alternative Energy Alternative Energy means energy used for fuel substitution; divided in 2 categories of theirs original resources; alternative energy from depleted resources such as coal, natural gas nuclear, peat and oil sand etc. and the other alternative energy from non-depleted resources which can be renewable such as solar, wind, biomass, hydro and hydrogen etc. In this article, it will only state about potential and status of alternative energy application.

273 Alternative Energy Study and Development is a study research monitoring development and demonstrate as well as promoting and disseminating alternative energy, which is clear energy and has no effect to the environment, and their resources have available locally such as wind energy, solar, biomass and others. The study research and development of alternative energy aims to disseminate efficient applications of alternative energy production, which are technically suitable for economic and social of metropolitan and urban users. This study also includes instrument, appliance and equipment development with highest efficiency. Alternative Energy Study and Development Activities are parts of alternative energy development plan. The example of projects, related directly under this plan, is energy study research project, which is related to rural development activity in PV battery Charging System for non-electrified Rural Villages Project. These activities are routine and supporting alternative energy technology development in term of technical theory and monitoring equipment as well as promoting and disseminating; which will support new study research project establishment including other related projects such as pre feasibility study, progress monitoring and cooperation with concerned agencies in developing of prototype, testing, analysis and assessment, and also support development of on going projects to fulfill their accomplishment as well as to promote and disseminate post project result for suitable application. Topic 3 Electricity 3.1 Electric energy refers to the energy created by the movement of electrons through a conductor, called Electrical Current which is produced when the two charges of opposite signs attract each other and move through the conductor that is copper. The movement of electrons is to flow from the positive terminal to the negative terminal. The unit for measuring an electric current is the ampere or ‚A‛.

274 Figure shows the movement of electrons in the conductor. The electric currents are divided into 2 types 1. Direct current (DC) is the unidirectional flow of electric charge to any appliances. Direct current is produced by sources such as a primary cell that is dry cells, or a secondary cell that is batteries, or DC generators. Figure shows the battery or the DC generator.

275 2. Alternating current (AC) is the flow of electric charge periodically reverses direction. The sources of AC are single-phase AC generators, or three-phase AC generators. Figure shows the AC generator. Voltage is the force that makes electrons move or electricity flow. The different voltages has a high amount of currents due to the unequal charges which are allowed to flow. The unit for voltage is the volt. Generally, it is denoted with symbol ‚V‛ on each appliance or power supply. Figure shows the current travels from high voltage to low voltage. Resistance is a material’s opposition to the flow of electric current. In addition, the value of resistance depends on types of materials. The unit for resistance is Ohm (ohm, W). It is also known as Ohms.

276 Conductors are materials that permit electrons to flow freely or have a low resistance such as copper, aluminum, gold, and silver which is the best conductor. It is denoted with symbol ‚G‛. The siemens is the unit of electric conductance. The calculation of conductivity based on the formula; G = 1/R ……………………. (6) Example A material has a resistance of 25 Ohms. Calculate the conductivity value of the material. According to the formula G = 1/R Representation G = 1/25 Answer G = 40 mS Insulators are materials or devices that do not allow electricity to pass through or have a high resistance which can resist the flow of current such as mica, glass, and plastic. 3.2 Ohm’s law The electrical current flowing in a circuit is produced by the voltage and the amount of current is controlled by the resistance. Therefore, the amount of current in the circuit depends upon the voltage and resistance. This circuit was discovered by George Simon Ohm, who was a German physicist and published it in 1826. The circuit is called Ohm’s law states that the electrical current (I) flowing in a circuit is proportional to the voltage (V) and inversely proportional to the resistance (R), which is shown below. Ampere …… (7) Example Calculate the amount of current of an electrical circuit that has voltage supply of 50 Volts and resistance of 5 Ohms. Solution According to the formula

277 I = 10 Amperes Ohm’s law Activity Experimental Tools 1. DC power supply set the output voltage to 0.3 V 2. Multimeter 3. Three different sizes of resistors 4. Wire The Experiment Figure: The circuit connection to prove the Ohm’s law 1. Take a 0.3-volt power supply connected with a resistor as shown in the figure. 2. Set 5 values of the power supply. Measure the amount of electrical current flowing through the circuit in each time of setting the output voltage. Records experimental results. V I 3. Calculate the value of 4. Write graph between the value of V and I 5. Calculate the slope. Compare to the value in No.3. Do the experiment following No. 1-4. to compare each resistor.

278 Question Does the value of V follow the Ohm’s law? Why? I 3.3 types of resistor connection Resistor connection refers to two or more resistors are connected between two points. In this lesson you will learn about types of connections that are a single connection, a parallel connection, and a compound connection. Moreover, the instances in this lesson will introduce the consideration and the simple calculation of a circuit as fast as possible in order to be a guideline in quickly calculating the circuit consisted of several resistors connected in a complex circuit and be confident in problem-solving about the general circuits. A series connection A series connection refers to the resistors are connected along a single path. One side of the second resistor is connected with one side of the third resistor. If there are the fourth or more resistors, they will be connected in series like a chain which is easily understandable by studying a diagram below. Figure shows a series connection. According to the figure, the resistors are connected in series; Rt = R1 + R2 + R3 Where: Rt = the sum of all the individual resistors R1, R2, R3 = the individual resistors

279 A parallel connection A parallel connection refers to the resistors are connected in parallel between two points. One side of all resistors is connected conjointly at one point of a circuit. Similarly, the other sides of all resistors are connected at the other ends of the circuit as you can learn from the figure shown below. Figure shows a parallel connection. According to the figure, the resistors are connected in parallel; 1/Rt = (1/R1 + 1/R2 + 1/R3) = (R2R3 + R1R3 + R1R2) / (R1R2R3) Therefore Rt = (R1R2R3) / (R2R3 + R1R3 + R1R2) Where: Rt = the sum of all the individual resistors R1, R2, R3 = the individual resistors Note When two resistors are connected in parallel and have the equal amount of resistance, the calculation of the total resistance is used either an amount of resistance (because of the equal amount) and divided by the number of the resistances, which are 2. Likewise, if the total resistances are ‚n‛ of resistors connected in parallel and each of them have the same amount. To calculate the sum of resistance by using one value of the resistance and divided by the number of resistors that are ‚n‛. Compound Circuits A compound circuit is made up of both series and parallel circuits. Thus, to calculate the values of electricity such as the electric currents, the voltages, the total resistance is based on the knowledge of series circuits, parallel circuits, and the Ohm’s law. Generally, there are 2 types of compound

280 circuits that are a series-parallel combination of resistors and a parallel-series combination of resistors as the figure shown below. Figure shows the DC combination circuit (Series-Parallel) To calculate the total value of resistance (RT), first you have to calculate the other total value of resistance (RT2) between the resistor 2 and the resistor 3 based on the formula of parallel circuits. Then, add up the RT2 to the RT1 according to the formula of series circuits. To determine the values of electric currents and voltages by calculating the value of circuits in the same methods of the series and parallel circuit calculation as stated above.

281 3.4 The calculation of the resistor’s value Series and Parallel Circuits The resistors connected in parallel will have the equal amount of potential difference across them. You will determine the equivalent resistance (Req) likewise there is one resistor as follows; You can use a symbol to represent in the equation of the resistors connected in parallel by 2 vertical lines ‚ || ‛ as shown below. The current flowing through each individual resistor connected in series is the same, but the potential difference of each resistor is not the same. Hence, the total potential difference across all the resistors is equal to the sum of the potential differences across each resistor. You can calculate the value of resistance equal to; R = R1 + R2+ R3 The resistors connected in both series and parallel can be separated to single part and calculated in each part as follows;

282 4 Band resistor color code calculators 4 Band resistor color code calculators are the most common type with the four bands are painted around the body of the calculators. The first two bands represent the digits of the resistance value; the third band is a multiplier (X) of the first two bands; and the fourth band indicates the tolerance of the value which will be of 2%, 5%, or 10%. The resistor color code table based on the standard Electronic Industries Alliance (EIA-RS-279) Color 1st Digit 2nd Digit 3rd Digit 4th Digit Temperature (Multiplier) (Tolerance) Coefficient Black 0 0 x 100 Brown 1 1 x 101 ±1% (F) 100 ppm/K Red 2 2 x 102 ±2% (G) 50 ppm/K Orange 3 3 x 103 15 ppm/K Yellow 4 4 x 104 25 ppm/K Green 5 5 x 105 ±0.5% (D) Blue 6 6 x 106 ±0.25% (C) Violet 7 7 x 107 ±0.1% (B) Gray 8 8 x 108 ±0.05% (A) White 9 9 x 109 Gold x 0.1 ±5% (J) Silver x 0.01 ±10% (K) None ±20% (M) Note: Red to violet are the colors of the rainbow where red is low energy and violet is higher energy.

283 Preferred value The commonly used resistors can be measured from the unit of milliohms to gigaohms in this range there are some values called the desired value produced. Besides, the common transistors do not have the ideal value practically. Thus, the tolerance of the value is indicated through the fourth band. 5 Band resistor color code calculator 5-band identification is used for higher precision resistors (the tolerance of the value is 1%, 0.5%, 0.25%, 0.1%). The first three bands represent the value of resistance; the fourth is the multiplier; the fifth stripe gives the tolerance. The quality 5-band precision resistors are found in the early model resistors or the special resistors whose tolerance of the value is the fourth band and the fifth band tell us the temperature coefficient. SMT resistors The surface mounted resistors indicate the value of resistance through numerical code. The surface-mount technology (SMT) is precisely marked with a 3-digit code. The first two digit represent the resistance and the third digit is the logarithm of 10, for instance, ‚472‛ refers to ‚47‛ indicates the resistance multiplied by 102 as 47 x 102 = 47 x 100 = 4700 Ohms. The higher precision resistors of SMT will represent the 4-digit code. The first three digits give us the resistance and the fourth digit is the power of 10. Measurement A resistor is a poor conductor; on the other hand, a good or perfect conductor such as superconductors has no resistance at all. Therefore, if you want to test your device that how accurate it is, the value of a resistor can be measured with an ohmmeter. The value of the device being measured is equal zero Ohms in all calibration (Figure 1). The best or quite good conductors are necessary for general electrical circuits. In the electronic jobs will use an electrical instrument, known as an ohmmeter to measure electrical resistance.

284 Figure 1: A good conductor has no resistance whose value being measured is equal zero Ohms. Experimental Activity: Resistors Objectives 1. Understand the reading of the resistor color code principles. 2. Read the resistor color codes correctly. Experimental tools 1. Resistors Resistor Experiment 1. According to the resistor color codes; brown, red, orange, read the value of resistance before the experiment. (Example) Read the resistance value by yourself = …………….. Ohms 2. Choose the provided resistors and record the resistance value. 3. According to the table below, write colors based on the color band in order to get the resistance value as determined and do the experiment by changing the color as written before in order to compare the results. 1st Color Band 2nd Color Band 3rd Color Band 30 Ohms 45 Ohms 53 Ohms

285 330 Ohms 680 Ohms 940 Ohms 1.2 Kiloohms 3.5 Kiloohms 120 Kiloohms 480 Kiloohms 1000 Kiloohms 1200 Kiloohms 3.5 Electricity in Daily Life Electricity is essential and plays important roles in our daily lives, from birth till death. We can utilize electricity in different areas such as lights, heat, energy, sound and etc. We must be very careful in utilizing electricity and know the right method as well as how to prevent hazard correctly. Here we will discuss the type of electricity and electrical equipments that we use in our daily life. Electricity in our daily life that we should know 1. Main Switch is the main equipment use to switch on and off the main electrical line circuit with all the internal line of the building. It is the first electrical circuit breaker in conducting electric into your home next to electrical meters. Main Switch consisted of disconnecting means and over current protective device. Function of the Main Switch is to control the safety in utilizing electricity, in the case where there is electric current overload or short circuit we can immediately switch off or remove the fuse to cut off the electric current from entering the building. 2. Breaker (circuit breaker) or automatic switch is equipment that can automatically switch on and off or disconnect electric circuit, by which the short circuit must not exceed the interrupting capacity (IC) of the device.

286 3. Fuse is one type of over current protection, it will automatically cut off electric circuit when there is electric current overflow that is more than the limit specified and when the fuse set to work, new fuse must be change. The fuse’s interrupting capacity must not be lower than the short circuit that runs through fuse. 4. Residual current breaker is an automatic switch that can quickly disconnect circuit within the specified time. When there is earth current leakage over the specified amount the residual current breaker is use as a preventive device along with the ground line system, to prevent danger from electric shock. 5. Ground line is an electric wire used to reduce the risk of electric shock. One end of the ground line must be connected to the earth ground and the other end is connected to the object or appliances that required electric potential to be neutral to the ground. 6. Socket-outlet or female connector is a receptacle for connectors from appliances. Normally, receptacle is installed on one place such as mounted on the wall of the building. 7. Plug or male connector is a terminal or connector from electric appliances to connect to the outlet so the electric appliances will work. 8. Electric appliances class 1 means general electric appliances that have enough thickness of the insulation for normal usage only, usually the outer shells of these appliances are made from metal. For these types of appliances the manufacturer must connect the ground line of the appliances to the metal so that it can be extends to the earth, then into main switch box through the ground line of the socket-plug. 9. Appliances class 2 or double insulated electricity appliances is one which has been designed in such a way that it does not require a safety connection to ground line. 10. Electric appliances class 3 means electric appliances that use with AC (alternating current) not more than 50 volt. These types of appliances do not require any ground line.

287 Prevention of electrical hazard and helping victims of electrical hazards 1. Preventing Electric Hazard Electrical cords and electric appliances must have insulations, the cable must be connected correctly and make sure that it is strong enough. When use for a long period of time the insulator may be frayed or damaged, torn or have loosen joint. If the users touch with the metal part may cause electric current through the body and may cause death. Primary preventions are as follow: 1. Check the insulation and the joint of the cords before use. 2. Use a screwdriver to tighten the joints of the cord and the equipment. Make sure they are in good condition and ready to use. 2. Giving first aid and moving victims of electrical hazard Connect appropriate size of electric wire from metal shield of the electric appliances into earth ground so that the current leakage can flow directly into ground. This will prevent the electricity users from getting electric shock. 3. Connecting ground line and other current leakage protection devices Current Leakage protection device Electricity leakage in general electric distribution systems can likely occur from utilizing it for a long period of time, as well as deterioration of insulation and various accidents may occur. No one knows when will there be leakage and short circuit, so it is important to install devices that detect leakage currents and disconnect fast enough before any danger could occur. Engineers found two methods in preventing leakage, which are: Method 1 Setting up ground line. When there are enough quantity of electric current leaking into earth ground causing the circuit breaker to cut off the circuit so there will be no electric current. Method 2 Use Residual current device Base on the principle of inducing electricity from the electric transformers during normal condition of equally inflow and outflow from the electricity device in the circuit. Magnetic line of force that occur in the steel rod from both primary coils are coiled equally, therefore cancel out and there is no electric current in the secondary coil. Though when there is an electric leakage both

288 electric wires will have unequal electric current causing the magnetic line of force in the steel rod to induce electric in the secondary coil transmitting signal to cut off the electrical circuit. Victims of electric shock may fainted, therefore those who are nearby or witnesses the incident must help correctly. First step quickly cut off the current. Second step use a non-conducting item to move the victim, such as a hose, dry clothes or dried wooden stick. Do not use your hand to touch the victim. If the victim is not breathing, quickly perform rescue breathing by laying the victim flat to the ground tilt the victim’s head back gently and lift the chin slightly. Pinch the victim’s nose and blow air into the mouth periodically. Blowing firmly and quickly approximately 10 times per minute until you can see the chest is rising and lowering. Continue giving recue breathing until help arrived or the victim has reached the hospital at which the victims will be given oxygen to help with the breathing as well as cardiac massage. Electric energy conservation Energy conservation Definition of energy conservation is producing and consuming amount of energy efficiently and economically. Energy conservation also helps reduce energy consumption, which economize business expenses and reduce environment problems that occur from the use and production of electricity sources. What is energy conservation? Energy conservation is the objectives under the Energy Conservation Promotion Acts B.E. 2535, prescribed that the target groups which are designated buildings and designated factory to provide infrastructure such as information, personnel, framework and etc. This is to conserve energy in accordance with the laws; also these energy conservation activities can be use as frameworks and guidelines to improve the efficiency of energy usage. Laws of energy conservation The Energy Conservation Promotion Act B.E. 2535 (1992) prescribed that the owner of designated buildings and designated factories must 1. Assign at least one person to take a full-time position at each designated building or designated factory.

289 2. To carry out energy conservation according to the prescribe standard. 3. Submit information on energy production, consumption, and conservation to the Department of Energy Development and Promotion. 4. Keep records of information on energy consumption and installation or modification of machinery or equipment that affects energy consumption and conservation. 5. Set targets and plans for energy conservation of the designated factory and submit to the Department of Energy Development and Promotion. 6. Audit and analyze operations to achieve such targets and plans for energy conservation. Details and procedures in number 2-6 will be announced as the Ministerial Regulations by summarizing the significant issues under the topic ‘Procedure in Energy Conservation’ as in accordance with the laws, procedures that will lead you to successful energy conservation and in accordance with the regulations prescribed by the law. Ways to Conserve Electric Energy Generally most home ‚electric appliances‛ often use high power, therefore users should have knowledge and know how to use electricity efficiently to reduce electric bills and reduce problems in utilizing power in the wrong way. This document will talk about some electric appliances that have never published before. Electric Water Heater Utilizing energy wisely and properly You should primarily choose a suitable electric water heater such as if you only need warm water to shower then you should install single-point electric water heater. You should choose water efficient showerhead as it can help save 25-75% of water. Use storage water heater with insulation this can help save 10 -20% energy. Avoid using electric tankless water heater because it will waste energy. Always turn off the valves and switch when not in use.

290 Television Ways to use television properly and save energy 1. In choosing television you should consider your need in utilizing it by considering from the size and the consumption of electric power. 2. Colored TV with the same system but different in size also consume electric power differently. In other words, bigger colored TV is more expensive and consume more electricity than the smaller colored TV such as - It will cost us 5% more in the electricity bill for the 16‛ TV with normal system than the 14‛ TV or - 20‛ TV will cost 30% in the electricity bill more than the 14‛ - A 16‛ remote control TV will cost 5% more in the electricity bill than the 14‛ or - 20‛ TV will cost 34% more in the electricity bill than the 14‛ - Within the same size colored TV with remote control system will consume more electricity than a normal colored TV. - A 16‛ colored TV with remote control will cost 5% more in the electricity bill than the normal TV - A 20‛ TV with remote control system will cost 18% more than a normal TV system. 3. Unplug the plug because internal systems of television always have electric supply moreover may cause danger when there’s lightning. 4. Turnoff the TV when not in use or set a timer so that it can automatically turn itself off. This is to help save electricity. 5. Should not leave the VDO player plugged when not in use because VDO player is always active, this will unnecessarily cost electric bills to be high. 6. Consider and plan TV programs you want to watch. Only watch programs that you’ve choose and if watching the same programs should only turn on 1 TV.

291 FAN How to save energy and use it properly Table fan has a lower price and use less electricity than a stand fan, this is because table fan has smaller motors and lower watts, but a stand fan will give more wind therefore these are things to be considered before buying a fan. 1. Considered according to the need and location such as if you only use alone or not more than 2 people will be using it, you should use table fan. 2. Unplug the outlet, especially fan with remote control system because the electric current will flow into the fan all the time to supply the electronics equipment. 3. Should choose the strength and speed of the wind to suit with the need and locations because the stronger the wind the more electric it will consume. 4. Turn off the fan when not in use so the motor can cool down and to prevent it from getting degenerate too soon. 5. Place the fan where there’s airflow because fan draw in air around itself from the back of the propeller then release the wind to the front. For example if the air around the fan is damp you’ll get hot and damp wind. Moreover, if place the fan where there’s airflow the motor can cool itself better and it won’t deteriorate too fast. Electric Kettle

292 How to save energy and use properly 1. Choose the model with efficient insulation 2. Fill the kettle with your desired amount of water. Do not fill above the MAX line as it will consume more electric and may damage the kettle. 3. Never operate the appliance empty or with insufficient water because it may cause short circuit and is very dangerous. 4. Unplug when not in use to reduce wasting electricity and should not leave the kettle plug in the socket all the time. If you don’t need to use hot water at that time but still need to use it intermittently leave the plug in the outlet. Do not pull in and out too often because the kettle can’t keep the heat long and when unplug the temperature slowly decreased. When you need to use the kettle again you have to plug it and boil it again which is a waste of energy. 5. When not in use disconnect the plug 6. Do not block the steam way 7. Check your appliances and temperature control equipment that it is in good condition. 8. Should not put in an air-conditioned room. Vacuum cleaner Using energy efficiently and properly 1. Should select the size of the appliances according to the need. 2. Materials such as carpet or clothes are dust reservoir therefore should use heavy duty or high watt vacuum cleaner. Dust is easier to remove from houses with wood, cement or marble floors so lower watt would best suit with these kind of floors and it will help save electricity as well. 3. Regularly clean the filters or dustbags; blocked filter or full dustbags will reduce suction power of the cleaner causing the motor to work harder and take more time to clean. This may cause the motor to be overheat and may burn. 4. Should use vacuum cleaner in a room with good airflow as it helps cool down the motor.

293 5. Do not vacuum up any water, liquid or damp dirt as well as sharp objects such as knives. Do not vacuum up anything, which has been burning or is still glowing e.g. cigarettes ashes or coal. The cleaner might catch fire or parts of the cleaner might be damage. 6. Select floorhead that suits with the type of dust or location. Crevice nozzles are used for vacuuming in tight spaces and in corners. Dusting brushes are used with lamp, ceiling, picture frames and etc. If used inappropriately may decrease the machine efficiency in vacuuming and waste more electric power. 7. Before vacuuming check that all parts and maker sure that they are tightly connected, otherwise the air may leak causing the motor to work harder and reduce suction power which may leads to overheat and the vacuum cleaner may burn. Air Conditioner Ways to save energy and use properly 1. Selecting appropriate size The size of the air conditioner for each room differs; generally on average the height of a room is 2.5-3 meters, which may roughly estimate from the following set. -Living room and kitchen are around 15 square meters/ ton of refrigeration - Bedroom with a roof as a ceiling around 20 square meters/ ton of refrigeration -Bedroom with ceiling as another room’s floor around 23 square meters/ton of refrigeration 2. Buying Air Conditioner - Choose air conditioner with well-known trademarks because we can be certain that the air conditioner has standard quality and that it is reliable. Significantly, when buying air conditioner we can consider from the cooling capacity and energy efficiency that are in the manufacturer catalog. - If the purchased air conditioner size does not exceed 25,000 BTU/ hour, buyers should choose the one with Label no.5 which certified that the appliance is high performance and save energy. The label can be clearly see on the appliances - If you need to buy an air conditioner that’s bigger that 25,00 0 BTU/hour choose the one that consume electricity not over 1.40 kilowatt per 1 ton of refrigerator or have EER

294 (energy Efficiency Ratio) not less than 8.6 BTU/hour/watt. This kind of information will be available in the manufacturer catalog. 3. Using air conditioner Using air conditioner properly helps the devices operate more efficiently and help save energy. Which can be done as follow: - Set appropriate room temperature for kitchen, living room, and dining room the temperature can be set not below 25 C. - We can decrease electric consumption at 15-20% if the temperature of the bedroom is set at 26-28 C. While sleeping human body doesn’t move much and tends to sweat less, therefore it wouldn’t be too hot if at a higher temperature. - Turn off the air conditioner when not in use. Set timer to turn off automatically if you know the exact time that you will not use the air conditioner. - Don’t block the air way of condensing unit as it will be difficult for the machine to release heat and causing it to work harder. - Don’t block the airway of fan coil unit with pictures or objects because the room will not be cold. - Only turn on the light that needed to be use and turn off every time when finish using it because some light bulbs and electric appliances release heat causing the temperature in the room to be higher. - Avoid using kitchen ware or other utensils with hot surface such as electric stove, electric kettle, pot in the air conditioned room. Food should be cook in the kitchen and bring into the room to eat. - When the room is not in use or before you turn on the air conditioner for about 2 hours, you should open the door and window so that fresh air can flow in, which help reduce odour. You don’t need to turn on the fan as it will make the air conditioner works harder. - Shut all the door and window properly while using air conditioner to prevent hot air from coming in because if hot air comes in the room will make the air conditioner work harder. - Should put any plants or dry your clothes in the air conditioned room because moistness from these things cause the air conditioner to work harder.

295 Lights Ways to save energy and use properly - Turnoff the light if not in use for more than 15 minutes this will help save electric and will not have any effects to the lifetime of the device for example during office or school lunch break or at home such as in the toilet, kitchen and etc. - Turn on and off the lights automatically by using device that set time or command automatically from the control system. - Use Occupancy Sensor, these kinds of devices are suitable with conference room, classroom, private workroom; normally comes in two types: Infrared and Ultra sonic. Brightness standard chart (IES) Brightness (Lux) 300 Type of area 300-700 500 100-200 100-300 General working area 300-500 100-300 Hallway 300-750 500-1,000 Classroom Hall way 50 Kitchen 200 shops/shopping Mall Restroom 100-500 Hotel 100-500 General area 100 Hospital Examination room 300-500 Residential : Bedroom headboard bahtroom living room stairways kitchen

296 Topic 4 Light 3.7 Light and the properties of light The primary source of light in our life is the sun that is the natural source. The moonlight we see at night is the Sun’s light that strikes on the moon’s surface and reflects to the earth. However, there are the man-made sources of light apart from the natural sources such as bulbs, lamps, and candles etc. Light is useful and important to living things. When a candle is lit in a dark room, we will see the flame because light reaches our eyes. We can see the other things in the room as the light of the flame strikes on their surfaces and reflects to our eyes. Light reaching our eyes or any areas appears to travel in a straight line; for example, setting up a lit candle in which you align three cardboard with a different position of holes of each, you will not see the flame. After aligning with the three holes, it is noticeable that if you thread a rope through the holes and pull it in a straight line, you will see the flame. It appears that ‚light travels in a straight line.‛ You can draw a straight line to demonstrate the beam of light, called a ray of light. To draw a straight line representing a ray of light by using a straight line represents a beam of light and an arrow shows directions. In other words, a pointing arrow tells the direction of light. To see any objects, there must be light from an object reflecting to our eyes which is divided into 2 cases; 1. When an object has its own light, it will emit light to our eyes directly. 2. If an object does not emit its own light, there must be light that is reflected from an object to our eyes. Light can pass through some objects. Alternatively, some objects do not allow

297 light to pass through. The types of objects based on the amount and characteristics of light passing through are divided into 3 types as follows; 1. Transparent object refers to objects which allow light passing through them without distorting it. You can see through a transparent object. Additionally, the object on the other side can clearly be seen. There are many types of transparent objects such as air, clear glass, water glasses, and clear plastic sheets etc. 2. Translucent object is objects that allow some light to pass through them but they distort it. When you see through a translucent object as a result the object on the other side can partially be seen such as oil-soaked paper, frosted glass, stencil paper or wax paper, and fog etc. 3. Opaque object is objects blocking all light from traveling through them, like fabric, wood boards, aluminum sheets, zinc sheets, thick paper, iron, and copper etc. We have previously learned that light is a form of electromagnetic wave. It can travel without a medium and travels in straight lines. In addition, the speed of light depends only on the medium it travels through. If the medium has the high optical density, light will travel slower through it. If light is unable to travel through the medium due to light absorption, reflection, or interference. These are the properties of light we are studying in this lesson. The properties of light The properties of light can be applied to create many things, for example, the reflection of light is used to make a reflecting cover for a fluorescent lamp, the refraction of light is employed to design a refractor which is made of glass or plastic to control the direction of light from a lamp, the principle of diffusion when light strikes a medium can be applied to make plastic sheet light covers to control the lamp brightness, the light absorption is used to build solar ovens and solar boilers, and the principle of interference is applied to cameras and video projectors. The properties of light as stated above are used in our daily life. Reflection Reflection refers to light striking an interface between two different media and reflecting to where it originated. The reflection is also dependent upon the nature of the interface, shiny or rough. Generally, if a ray of light strikes a flat, shiny surface, then it will reflect at the same angle as shown in figure A. These characteristics of objects include polished aluminum, iron coated with

298 chromium, gold, silver, and mirror etc. On the other hand, if light reflects off on a rough surface, it will cause each of the light rays diffused as shown in figure B, for instance, cement rendered wall, and white paper. Most of object surfaces are mixed up depending on how much shiny or rough material they are. The reflection of light is shown in figure A and B. AB Figure A shows the reflection off of a smooth surface. Figure B shows the reflection off of a rough surface. The law of reflection 1. The incident ray, the normal line, and the reflected ray lie in the same plane. 2. The angle of incidence is equal to the angle of reflection. Refraction Refraction is the change in direction of a wave due to a change in passing from one medium to another; for instance, light passes from air into water as shown in the figure. Figure shows the refraction of light.

299 Things you should know about the refraction of light. - The frequency of light remains constant while the wavelength and the speed of light will change. - The path of light will lie in the same plane if the light strikes the interface between two media at a 90 degree angle. In contrast, the light path will not lie on the same plane if the light does not strike the interface between two media at a 90 degree angle. Here are the examples of the benefits of refraction; for instance, light refractors which are made of glass or plastic in order to control the direction of light. As shown in the figure, the light from the headlights spread out in all directions. However, when it passes through the light refractors, it will travel in the same direction such as the headlights of cars and motorcycles. As shown in the figure. Light travels through the headlights in the same direction.

300 Light diffusion The light diffusion is the white light, consisting of many frequencies of light, passing through a prism where 2 times of deviations occur (at the interface of the prism both striking on and dispersing out). The prism will orderly separate the white light into different colors based on their wavelengths and frequencies called spectrum. Rainbow is a diffusion of light. The white light enters the raindrop, reflects off of the side of the drop and exits. Then, the light deviates to the air and disperses into different colors. The light will diffuse when it strike the interface of media. The benefits of the light diffusion striking the media are to make plastic sheet light covers to control the light bulb brightness or the brightness of closed tube lamps. A rainbow Transmission Transmission refers to the light traveling through the medium to the other end with the constant frequency. Objects that have the property of transmission include glass, crystal, clear plastic, water and liquid.