This chapter complies with on native the critical chapter where we pointed out that heat deserve to be "lost" as power is transferred to the surroundings. This thing now explains that within a system, there is useful energy i m sorry is transferred to the wanted object or place, however no procedure is 100% efficient. Power can be transferred to the surroundings quite than to the thing or component of the device that you want it to transfer to. This is considered a garbage of energy and also systems space designed to shot minimize this garbage so that they are an ext efficient. Over there is constantly some loss of energy (wasted energy) and so over there are always by-products to power production. Some of the byproducts are harmful come the environment.

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Important to keep in mind is that CAPS makes the complying with statement:

"The output energy in a system is constantly less 보다 the input energy, due to the fact that some of the power escapes come the environment."

This is not correct as the output energy is always equal come the input energy as power is conserved in ~ systems. The statement have to rather state:

"The output power in a system is constantly less than the input energy, because some that the power escapes come the environment."

The wasted energy is still component of the output energy from the system, the is simply not useful.

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

Tasks

Skills

Recommendation

Activity: useful outputs from energy systems

Accessing and also recalling information, identifying and also classifying

Suggested

Activity: energy transfers in systems

Accessing and recalling information, identifying and also classifying

CAPS suggested

Activity: illustration Sankey diagrams

Interpreting, sorting and classifying, interacting information graphically

Suggested

Activity: Researching power transfers

Researching, accessing and also recalling information, interpreting, sorting and also classifying, communicating information; written, graphically

CAPS suggested


What type of useful energy output execute some solution produce? What is supposed by "wasted" energy? What is a Sankey diagram? just how do we attract Sankey diagrams?

Useful and wasted energy


Sankey diagram input output
The learners will certainly not have actually seen Sankey diagrams before. Girlfriend should describe the usefulness the representing processes using pictures. Illustrations do a quick, visual affect on the viewer which renders it less complicated to know a process. A Sankey chart is a visual depiction of an energy process showing the entry energy and the calculation energy. Sankey diagrams need to be drawn neatly and also as close to scale as possible. Take the moment to attract several instances on the plank so that the learners see that all energy processes have much more than one output power type.


This term we have been looking at power transfers within systems. Systems have an entry energy and also an output energy. Solution such as appliances, tools, vehicles and machines administer us v a advantageous output. Let"s look in ~ some instances to identify what these outputs space in some systems.


valuable outputs from power systems

INSTRUCTIONS:

Look at every of the photos and also identify what is helpful to use from this system.

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

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An electric iron.

System

What beneficial output go it carry out us with?

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


System

What useful output walk it carry out us with?

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

Light

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

Movement

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An electric iron.

Thermal energy


What to be the input for each of these systems?


Electricity/electrical energy.


anytime we use an appliance or a device we room transferring power from one object to another. Not all the energy is transferred where we desire it, a many it is moved to the surroundings wherein it walk not aid us attain our aims. The power which is transferred to the next site is "wasted".


Watch just how this coco rabbit melts beneath an energy-inefficient light bulb.


We deserve to use a Sankey diagram to display how the energy is moved in a system. This offers us a picture of what is happening and shows the entry energy and also how the output energy is comprised of useful energy (arrow in ~ the top) and wasted power (arrow going to the bottom). Have actually a look at the adhering to general example.

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Sankey diagrams are called after the irish Captain Matthew Sankey, who an initial used this kind of chart in 1898 in a publishing on the energy performance of a steam engine.


The width of the arrows tell united state something in this diagrams. The input energy is the width of the original arrow. The width of both the output power arrows (useful and wasted) include up to the broad of the entry arrow. Why perform you think this is so? Think ago to what friend learned around energy within equipment in chapter 2.


This is because energy is neither produced nor destroyed, yet conserved within a system. So the input must equal the output power in a system.


Sankey diagrams are drawn to scale so the the broad of the arrows gives us a intuitive idea of just how much energy is useful and also how lot is wasted. In the chart above, you have the right to see that only a small component of the input energy was useful and also a big amount the the input to be wasted by being transferred to the surroundings. An effective system is one whereby the helpful output power is just slightly smaller sized than the intake energy. One inefficient system has a the majority of wasted energy. Perform you think this is an reliable energy system? Why?


No, the is not reliable as a lot of the energy is wasted.


This brings us to ours next point of how effective an power system is. If the wasted power is much larger than the beneficial energy output, then the mechanism is not energy efficient. The above Sankey diagram actually shows the power transfers for a light bulb. You established the advantageous energy output as irradiate in the critical activity. What execute you think the wasted energy output is? whereby does it go?


that is shed as heat, as power is transferred to the neighboring air.


perform you watch that an incandescence light pear is actually no a really efficient system? This is because a most the power is shed as warm as power is transferred to the surroundings. Is over there something more efficient? Look in ~ the picture of a fluorescent irradiate bulb.

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A fluorescent irradiate bulb.

A fluorescent light pear is much more efficient than incandescent light bulbs which usage a heated cable to develop light. Many of the power is shed as the is transferred to the bordering air indigenous the steel filament. In a fluorescent irradiate bulb, less power is lost to the surroundings and more energy is transferred to advantageous light energy. Use this details to attract a Sankey diagram because that a fluorescent light bulb in the an are below.


Learner"s diagram have to look together follows:

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Let"s look at at another example. Look in ~ the lady in the photo using an electrical drill. The electrical energy indigenous the drill is transferred to the drill little bit as kinetic energy. The drill bit turns and drills right into the metal. Yet the drill also makes a lot of noise. Power is offered to do sound and also the drill bits get hot, so few of the power is converted right into thermal energy. This method that few of the electrical energy has been transferred to the surroundings as sound and also thermal energy. This is energy that has been "wasted" due to the fact that the sound and also thermal power are not useful to us.

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A lady using an electrical drill to do a hole in an aeroplane part.

Complete the complying with Sankey chart by composing in what the energy input is, and also then the energy outputs.

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Learner"s Sankey diagram need to look as adheres to with the labels:

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In bespeak to attract a Sankey diagram you should think carefully about the input energy and also how the input energy is moved to the surroundings. Let"s practice this a bit much more in the adhering to activity.


energy transfers in systems

INSTRUCTIONS :

Look in ~ the adhering to diagrams/photos that appliances. Complete the tables mirroring the power transfers for each diagram/photo. The an initial one has actually been completed because that you.
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Filament in a light bulb.

Energy INPUT

Useful power OUTPUT

Wasted energy OUTPUT


Energy INPUT

Useful energy OUTPUT

Wasted energy OUTPUT

electricity

light

thermal energy


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burn candles.
Energy INPUT

Useful energy OUTPUT

Wasted energy OUTPUT


Energy INPUT

Useful energy OUTPUT

Wasted power OUTPUT

potential energy in wax

light

thermal energy


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An electric beater.
Energy INPUT

Useful power OUTPUT

Wasted energy OUTPUT


Energy INPUT

Useful power OUTPUT

Wasted power OUTPUT

electricity

movement/kinetic energy

sound, heat energy


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A auto engine.
Energy INPUT

Useful power OUTPUT

Wasted energy OUTPUT


Energy INPUT

Useful power OUTPUT

Wasted power OUTPUT

petrol/potential energy from burn fuel

kinetic energy

thermal energy, sound


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Welding steel together.
Energy INPUT

Useful power OUTPUT

Wasted energy OUTPUT


Energy INPUT

Useful energy OUTPUT

Wasted energy OUTPUT

electrical energy

thermal energy

light, sound


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Athletes running.
Energy INPUT

Useful energy OUTPUT

Wasted energy OUTPUT


Energy INPUT

Useful power OUTPUT

Wasted power OUTPUT

potential power in food

kinetic energy

thermal energy, sound


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A television.
Energy INPUT

Useful energy OUTPUT

Wasted energy OUTPUT


Energy INPUT

Useful energy OUTPUT

Wasted energy OUTPUT

electrical energy

light, sound

thermal energy


now that us have established the energy transfers in every system and also the input and also output energy, let"s practice drawing some an ext Sankey diagrams.


Video on illustration a an easy Sankey diagram.


drawing Sankey diagrams

Let"s look at the instance of a filament light pear to draw a Sankey diagram. A filament irradiate bulb only uses about 10101010101010101010% of the input energy to generate light, the rest is "wasted" because it warms increase the neighboring air there is no producing any kind of light. This method that ours Sankey diagram must split into 2 parts: one for the light and also one for the thermal energy which is moved to the surroundings (heat). The heat energy arrow must it is in 90% of the broad of the intake arrow and also the light arrow must be 10% that the width of the entry arrow.

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INSTRUCTIONS:

Now draw a Sankey diagram for some of the appliances from the critical activity, which are detailed below. A summary of the power transfers has been provided for every appliance. Concentrate on showing exactly how the input energy is break-up between valuable energy and wasted energy. Remember the the width of the arrow must present how much power is transferred. A thick arrow method a huge amount that energy, a thin arrow method a small amount the energy. Present the various input and also output energies and also the percentages.

Electric beater:

The electrical beater move 70% that the input energy to kinetic power to win the food and 30% is wasted output energy in the type of thermal energy and also sound.

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Car engine:

The auto engine transfers only 30% that the input power to move the car and 70% is wasted as sound and also thermal energy.

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Television:

The television provides 80% that the input energy to produce the images on the screen and also sound and also 20% is wasted together thermal energy.

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QUESTIONS:


This is a research activity. If her learners have access to the web and/or a library then permit them to invest some time researching the energy transfers in a strength plant and a vehicle engine. If her learners perform not have accessibility to the net then it would certainly be a great idea to print out some information from miscellaneous websites that deserve to be handed out to the class. You could let the printed info circulate v the class so the you carry out not require as many copies. This will save on file and printing costs.

In this activity, they will first see just how the wasted energy can it is in in much more than one type and exactly how to represent this in a Sankey diagram because that a auto engine. Learners will certainly then research a strength plant. Friend can acquire the learners to job-related in groups to uncover the information but make certain that each learner is able to create their very own paragraph. This will give you a sense of whether or no the student has understood 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 Sankey diagrams, us just had actually one arrow for wasted power output, yet it can split into much more than one arrowhead to represent the different ways in which energy is wasted. There could likewise be more than one arrow for the beneficial energy, for example in the TV diagram above, light and sound space both useful and also could be represented by two arrows.


In the last activity we looked in ~ the energy transfers in a auto engine. However, we only offered one arrowhead to represent the wasted energy. Us can show a difference in between the methods in which energy is wasted in a Sankey diagram. Usage the adhering to information to label the Sankey diagram:

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

Only 30% that the energy is transferred to advantageous output power as movement.

About 70% that the energy is transferred to the next site in the kind of heat energy and sound. Few of the power is shed in cooling under the engine.

40% is lost as thermal to the surroundings.

20% is lost in cooling the engine.

10% is lost as sound.

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This is the labeled Sankey diagram:

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In a power station, energy is transferred v the mechanism in stimulate to produce electricity. Throughout the move of energy through the system, some of the energy is wasted.

Use the web or other resources to find the various ways in which energy is moved to the surroundings as wasted energy during the manufacturing of electrical energy in a power plant.

Write a brief paragraph to define the power transfers. Exactly how is the input energy transferred with the system and also where is the wasted power lost?


The i should incorporate the complying with information:

charcoal is burnt and the energy is transferred to the water and also used to boil the water. Several of the power is lost during this process. The vapor from the boiling water is provided to turn the turbine. The kinetic power of the heavy steam is moved to the turbine. Few of the power is lost to the surroundings together sound and also thermal energy. The kinetic energy of the turbine is transferred to the generator. Few of the energy is lost to the surroundings together sound and thermal energy. The kinetic power of the generator is supplied to generate electricity.


draw a Sankey diagram because that the energy transfers.


an instance for a Sankey diagram because that a power plant is offered below. Friend can additionally see what learners have found out and then attract one top top the plank to illustrate the transfers.

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Remember, power is measure in joules (J).


power entering a system is called the intake energy. The energy is moved in a mechanism to administer a helpful output energy. Tools, appliances, vehicles and also machines all provide useful power outputs. Not all of the input energy is moved to a beneficial output. Several of the power is wasted or lost. The beneficial output is because of this less 보다 the input energy as several of the output energy is wasted. An example is a irradiate bulb whereby the entry is electricity and also the valuable output is light. However, a large amount that the energy is shed to the surroundings together thermal energy. The efficiency of a device is figured out by just how much the the input energy is moved to valuable output energy. The higher the wasted calculation energy, the less reliable the system. A Sankey chart is offered to present the power transfers in a system. In a Sankey diagram, the arrows stand for the part of the input energy which is transferred to beneficial energy output and also the section which is moved to the surroundings and wasted.

Concept map

Complete the principle map by offering two instances of systems where energy is transferred to the surroundings and also "wasted" together sound and also thermal energy, and one example of whereby the wasted power output is light.

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Teacher"s version. The instances given here are not the only examples. Learners have the right to use any type of of the examples disputed in the chapter which space appropriate.

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Revision inquiries
attract a simple Sankey diagram to present the energy transfers in a device where the wasted energy output is an ext than the beneficial energy output. <4 marks>

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In the chapter, learners used percentages to attract their Sankey diagrams. The following is an extension and also starts off with a an easy example which castle have already seen in the chapter, namely a light bulb, yet the energy transfers were stood for as percentages. In the an initial example here, we now start off through 100 J instead of 100%. The Sankey diagram will be straightforward to draw. However, in the subsequent examples, the input power is much more than 100 J. Learners perform not need to calculate the percentages, yet the thickness the the arrows must be representative the the lot transferred.


for each that the adhering to situations, draw a labelled Sankey chart to display the amount of intake energy, useful energy and also wasted energy.

An electrical torch switch 100 joules (J) of electrical energy come 10 J of light energy and also 90 J of heat 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 form of sound and also 50 J is heat energy. <3 marks>

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A tv set.


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a. The potential power from the batteries in the torch is moved to the filament of the bulb. The power is transferred to the surroundings together thermal energy and also light. Most of the power is moved as thermal power which is no useful and only few 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 room useful since they space the images and sounds we desire to hear. The warm is wasted energy.

c. The power from the hair dryer is used to warm the air and dry ours hair. 2 thirds that the energy is helpful thermal energy but one third is transferred as sound, i beg your pardon is not advantageous to us.

See more: What Is The Climax Of The Outsiders Plot Diagram, The Outsiders Plot Analysis


An electrical geyser transfers electrical energy to thermal power in the water particles as the water is warmed up. The advantageous output is the thermal energy to warm the water. However, some of this thermal energy can escape native geyser come the surroundings. This is as such wasted. In bespeak to do the geyser system more efficient so the the useful energy output is greater and the thermal energy loss is minimized, the geyser should have actually an insulating covering, come reduce energy transfer to the next site by conduction.