This chapter adheres to on from the last chapter where we pointed out that heat can be "lost" as power is transferred to the surroundings. This chapter now explains that within a mechanism, there is helpful energy which is moved to the desired object or location, however no process is 100% reliable. Energy can be transferred to the surroundings rather than to the object or part of the mechanism that you desire it to carry to. This is considered a waste of energy and devices are designed to try minimize this waste so that they are even more effective. Tright here is constantly some loss of power (wasted energy) and so there are always byproducts to energy production. Several of the by-products are harmful to the environment.

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Important to note is that CAPS provides the adhering to statement:

"The output power in a device is constantly less than the input energy, because some of the energy escapes to the setting."

This is not correct as the output power is always equal to the input energy as power is conserved within devices. The statement should rather state:

"The output power in a system is constantly less than the input power, bereason some of the power escapes to the atmosphere."

The wasted power is still component of the output energy from the device, it is simply not helpful.

1.1 Useful and also "wasted" energy (3 hours)

Tasks

Skills

Recommendation

Activity: Useful outputs from power systems

Accessing and recalling indevelopment, identifying and also classifying

Suggested

Activity: Energy transfers in systems

Accessing and recalling information, identifying and classifying

CAPS suggested

Activity: Drawing Sankey diagrams

Interpreting, sorting and classifying, communicating indevelopment graphically

Suggested

Activity: Researching energy transfers

Relooking, accessing and recalling information, interpreting, sorting and also classifying, connecting information; created, graphically

CAPS suggested


What kind of helpful power output execute some systems produce? What is intended by "wasted" energy? What is a Sanvital diagram? How execute we attract Sanessential diagrams?

Useful and wasted energy


Sanvital diagram input output
The learners will certainly not have seen Sankey diagrams prior to. You should describe the usefulness of representing procedures utilizing images. Illustrations make a quick, visual affect on the viewer which renders it easier to understand a process. A Sankey diagram is a visual representation of an power procedure showing the input energy and the output power. Sancrucial diagrams need to be drawn neatly and also as cshed to range as possible. Take the moment to attract numerous examples on the board so that the learners see that all energy processes have actually even more than one output power kind.


This term we have been looking at energy transfers within systems. Solution have an input power and an output power. Solution such as appliances, tools, vehicles and also makers administer us via a helpful output. Let"s look at some examples to recognize what these outputs are in some units.


Useful outputs from energy systems

INSTRUCTIONS:

Look at each of the photos and recognize what is useful to use from this system.

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An electric fan.http://www.flickr.com/photos/_wick/5861380711/

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An electrical iron.

System

What useful output does it administer us with?

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A light bulb.http://www.flickr.com/photos/nikonfilm35/4209619566/


System

What valuable output does it administer us with?

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A light bulb.http://www.flickr.com/photos/nikonfilm35/4209619566/

Light

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An electrical fan.http://www.flickr.com/photos/_wick/5861380711/

Movement

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An electric iron.

Thermal energy


What was the input for each of these systems?


Electricity/electric power.


Whenever we use an appliance or a maker we are moving energy from one object to an additional. Not all the power is transferred wbelow we want it, many it is moved to the surroundings where it does not help us achieve our aims. The energy which is moved to the surroundings is "wasted".


Watch how this cacao rablittle melts beneath an energy-ineffective light bulb.


We have the right to use a Sanvital diagram to show exactly how the energy is moved in a system. This gives us a picture of what is happening and also shows the input power and how the output energy is comprised of useful energy (arrowhead at the top) and also wasted power (arrow going to the bottom). Have a look at the following basic example.

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Sanvital diagrams are called after the Irish Captain Matthew Sanvital, who first supplied this kind of diagram in 1898 in a publication on the energy efficiency of a vapor engine.


The width of the arrows tell us somepoint in these diagrams. The input energy is the width of the original arrowhead. The width of both the output power arrows (helpful and also wasted) add as much as the width of the input arrowhead. Why execute you think this is so? Think back to what you learned about power within units in Chapter 2.


This is bereason energy is neither produced nor destroyed, but conserved within a system. So the input should equal the output power in a system.


Sankey diagrams are attracted to range so that the width of the arrows offers us a visual concept of how much energy is beneficial and also exactly how a lot is wasted. In the diagram over, you deserve to view that only a small component of the input energy was advantageous and a big amount of the input was wasted by being moved to the surroundings. An effective mechanism is one wbelow the helpful output energy is just slightly smaller sized than the input power. An ineffective system has many wasted energy. Do you think this is an efficient energy system? Why?


No, it is not reliable as many the energy is wasted.


This brings us to our following point of just how efficient an power system is. If the wasted energy is much bigger than the valuable energy output, then the device is not energy efficient. The over Sanessential diagram actually mirrors the energy transfers for a light bulb. You established the valuable power output as light in the last activity. What perform you think the wasted energy output is? Wbelow does it go?


It is lost as warm, as power is transferred to the neighboring air.


Do you check out that an incandescent light bulb is actually not a very efficient system? This is because the majority of the power is lost as warmth as energy is moved to the surroundings. Is tbelow something even more efficient? Look at the photo of a fluorescent light bulb.

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A fluorescent light bulb.

A fluorescent light bulb is a lot more reliable than incandescent light bulbs which use a heated wire to develop light. Most of the energy is shed as it is moved to the surrounding air from the steel filament. In a fluorescent light bulb, much less energy is shed to the surroundings and more energy is transferred to helpful light energy. Use this information to draw a Sanessential diagram for a fluorescent light bulb in the room listed below.


Learner"s diagram must look as follows:

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Let"s look at an additional instance. Look at the lady in the photo making use of an electrical drill. The electric energy from the drill is transferred to the drill bit as kinetic power. The drill bit turns and also drills right into the metal. But the drill likewise renders a lot of noise. Energy is used to make sound and also the drill bits obtain hot, so some of the energy is converted right into thermal power. This implies that some of the electric power has been moved to the surroundings as sound and also thermal energy. This is power that has actually been "wasted" bereason the sound and thermal energy are not useful to us.

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A lady making use of an electrical drill to make a hole in an aeroaircraft component.

Complete the adhering to Sankey diagram by composing in what the energy input is, and also then the energy outputs.

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Learner"s Sanessential diagram must look as follows with the labels:

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In order to draw a Sancrucial diagram you must think very closely around the input energy and also how the input energy is moved to the surroundings. Let"s practice this a little bit more in the following activity.


Energy transfers in units

INSTRUCTIONS :

Look at the complying with diagrams/photos of appliances. Complete the tables reflecting the power transfers for each diagram/photo. The first one has been completed for you.
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Filament in a light bulb.

Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT


Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT

electricity

light

thermal energy


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Burning candles.
Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT


Energy INPUT

Useful Energy OUTPUT

Wasted energy OUTPUT

potential power in wax

light

thermal energy


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An electrical beater.
Energy INPUT

Useful Energy OUTPUT

Wasted energy OUTPUT


Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT

electricity

movement/kinetic energy

sound, thermal energy


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A automobile engine.
Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT


Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT

petrol/potential power from burning fuel

kinetic energy

thermal power, sound


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Welding steel together.
Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT


Energy INPUT

Useful Energy OUTPUT

Wasted energy OUTPUT

electric energy

thermal energy

light, sound


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Athletes running.
Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT


Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT

potential power in food

kinetic energy

thermal power, sound


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A television.
Energy INPUT

Useful Energy OUTPUT

Wasted power OUTPUT


Energy INPUT

Useful Energy OUTPUT

Wasted energy OUTPUT

electric energy

light, sound

thermal energy


Now that we have determined the power transfers in each device and also the input and output power, let"s practice drawing some even more Sancrucial diagrams.


Video on drawing a basic Sankey diagram.


Drawing Sanvital diagrams

Let"s look at the example of a filament light bulb to attract a Sanessential diagram. A filament light bulb only offers around 10101010101010101010% of the input energy to geneprice light, the rest is "wasted" because it warms up the surrounding air without developing any kind of light. This means that our Sanessential diagram need to separation right into 2 parts: one for the light and also one for the thermal energy which is transferred to the surroundings (heat). The thermal energy arrowhead need to be 90% of the width of the input arrow and also the light arrowhead have to be 10% of the width of the input arrow.

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INSTRUCTIONS:

Now draw a Sanessential diagram for some of the appliances from the last task, which are detailed below. A description of the power transfers has actually been offered for each appliance. Concentrate on mirroring exactly how the input energy is separation between helpful energy and also wasted energy. Remember that the width of the arrowhead need to show how a lot power is transferred. A thick arrow means a large amount of energy, a thin arrowhead means a tiny amount of power. Show the miscellaneous input and output energies and also the percenteras.

Electric beater:

The electrical beater transfers 70% of the input power to kinetic energy to beat the food and also 30% is wasted output energy in the develop of thermal power and sound.

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Car engine:

The automobile engine transfers just 30% of the input power to move the vehicle and also 70% is wasted as sound and also thermal energy.

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Television:

The television provides 80% of the input energy to create the imperiods on the display and also sound and 20% is wasted as thermal power.

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QUESTIONS:


This is a research study task. If your learners have accessibility to the internet and/or a library then enable them to spend some time researching the energy transfers in a power plant and also a automobile engine. If your learners do not have actually access to the internet then it would certainly be a great principle to print out some indevelopment from assorted websites that have the right to be handed out to the class. You might let the printed indevelopment circulate via the course so that you execute not need as many type of duplicates. This will certainly conserve on paper and printing costs.

In this task, they will certainly initially view how the wasted energy can be in even more than one create and how to reexisting this in a Sancrucial diagram for a car engine. Learners will certainly then research study a power plant. You deserve to gain the learners to work-related in groups to uncover the information yet make sure that each learner is able to compose their very own paragraph. This will provide you a sense of whether or not the learner has interpreted what they have actually researched.

Here is a resource for reference: http://www.bbc.co.uk/schools/gcsebitesize/science/21c_pre_2011/energy/generatingelectricityrev4.shtml


In our previous Sanessential diagrams, we just had actually one arrowhead for wasted power output, yet it have the right to separation right into even more than one arrowhead to reexisting the different means in which energy is wasted. Tright here might likewise be even more than one arrowhead for the useful energy, for example in the TV diagram over, light and also sound are both advantageous and can be represented by 2 arrows.


In the last task we looked at the energy transfers in a car engine. However, we just supplied one arrow to reexisting the wasted power. We deserve to display a difference between the methods in which energy is wasted in a Sanessential diagram. Use the complying with indevelopment to label the Sanvital diagram:

The input energy in a automobile engine is provided by the combustion of petrol.

Only 30% of the power is transferred to beneficial output power as movement.

About 70% of the power is moved to the surroundings in the develop of thermal power and also sound. A few of the energy is lost in cooling down the engine.

40% is shed as thermal to the surroundings.

20% is shed in cooling the engine.

10% is shed as sound.

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This is the labeled Sancrucial diagram:

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In a power terminal, energy is transferred with the device in order to produce electrical energy. Throughout the transfer of energy via the system, some of the power is wasted.

Use the internet or various other sources to find the different means in which energy is moved to the surroundings as wasted energy throughout the production of electricity in a power plant.

Write a brief paragraph to define the power transfers. How is the input energy transferred with the mechanism and where is the wasted energy lost?


The paragraph need to incorporate the following information:

Coal is charred and also the energy is moved to the water and also used to boil the water. Several of the energy is lost throughout this process. The vapor from the boiling water is supplied to rotate the wind turbine. The kinetic power of the heavy steam is transferred to the turbine. A few of the energy is lost to the surroundings as sound and thermal energy. The kinetic power of the turbine is transferred to the generator. Some of the power is lost to the surroundings as sound and thermal power. The kinetic power of the generator is supplied to geneprice power.


Draw a Sanessential diagram for the energy transfers.


An instance for a Sankey diagram for a power plant is offered below. You have the right to likewise watch what learners have actually found out and also then draw one on the board to highlight the transfers.

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Remember, power is measured in joules (J).


Energy entering a system is referred to as the input energy. The energy is moved in a system to provide a helpful output energy. Tools, appliances, vehicles and makers all provide advantageous energy outputs. Not every one of the input energy is moved to a helpful output. A few of the energy is wasted or shed. The beneficial output is therefore much less than the input power as some of the output power is wasted. An instance is a light bulb where the input is electricity and also the valuable output is light. However, a large amount of the energy is shed to the surroundings as thermal energy. The efficiency of a system is identified by just how a lot of the input power is moved to valuable output power. The better the wasted output energy, the much less reliable the mechanism. A Sankey diagram is used to show the power transfers in a device. In a Sankey diagram, the arrows represent the portion of the input energy which is transferred to beneficial energy output and the percent which is moved to the surroundings and wasted.

Concept map

Complete the idea map by giving two examples of systems where power is moved to the surroundings and also "wasted" as sound and also thermal power, and one instance of wright here the wasted power output is light.

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Teacher"s version. The examples given below are not the just examples. Learners have the right to use any type of of the examples questioned in the chapter which are correct.

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Revision inquiries
Draw a straightforward Sancrucial diagram to present the energy transfers in a mechanism wright here the wasted power output is more than the advantageous energy output. <4 marks>

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In the chapter, learners offered percentperiods to attract their Sancrucial diagrams. The adhering to is an expansion and starts off through a basic instance which they have actually currently watched in the chapter, namely a light bulb, yet the power transfers were represented as percentperiods. In the initially example here, we currently start off through 100 J instead of 100%. The Sankey diagram will certainly be straightforward to attract. However before, in the subsequent examples, the input power is more than 100 J. Learners perform not should calculate the percentperiods, but the thickness of the arrows must be representative of the amount transferred.


For each of the following instances, attract a labelled Sankey diagram to present the amount of input power, valuable energy and also wasted energy.

An electrical torch converts 100 joules (J) of electrical power to 10 J of light power and also 90 J of thermal energy. <3 marks>

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An electric torch.

A television has an power output of 500 J. 400 J is in the form of light. 50 J is in the create of sound and 50 J is thermal power. <3 marks>

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A television set.


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a. The potential energy from the batteries in the torch is transferred to the filament of the bulb. The energy is transferred to the surroundings as thermal energy and also light. Most of the power is moved as thermal power which is not valuable and only some of the power is transferred as light.

b. The power from the TV is moved to the surroundings as thermal energy, sound and also light. The light and sound are useful because they are the imeras and sounds we desire to hear. The warm is wasted energy.

c. The power from the hair dryer is supplied to heat the air and dry our hair. Two thirds of the power is beneficial thermal power yet one third is transferred as sound, which is not useful to us.

See more: Difference Between Chemical Formula And Chemical Equation, Chemical Symbol


An electric geyser transfers electrical power to thermal power in the water pshort articles as the water is warmed up. The useful output is the thermal energy to heat the water. However before, some of this thermal energy deserve to escape from geyser to the surroundings. This is therefore wasted. In order to make the geyser mechanism even more effective so that the beneficial energy output is higher and also the thermal energy loss is decreased, the geyser need to have actually an insulating spanning, to alleviate power carry to the surroundings by conduction.