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energy transferred from energy to
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energy transferred from energy to
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energy transferred from energy to
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this is quite a long activity with many examples but it leads into the technology project a bit later where learners have to use an electric circuit to produce light movement sound or heat .
this activity will act as a stimulus for ideas for the project .
each of the examples in the previous activity uses an electric circuit to provide us with energy where we need it whether it is light on the street sound for our radio or heat in a building .
or even in some toys and models such as a car racing game or model electric train set !
we can say that electrical appliances can solve problems for us .
they are able to transfer electricity so that another useful form of energy is released .
at this point learners have learnt adequate concepts related to electricity to give them a technology design project to do .
they can work individually or in teams of 3 4 .
ideally though each learner should design and make their own system to fully engage with the task .
learners will apply what they learnt by first discussing designing and drawing a plan of how to use a circuit to produce movement light sound or heat .
it is generally more difficult to produce heat energy using cells but this can be explored by learners if they feel they are up to it .
then they will implement their design and make the structure and then present it to the class .
communication is a vital skill and forms part of the technology design process .
communication can be written or verbal but in this case learners must verbally present their designs to the class .
the model that learners build need not be to scale .
possible designs include a steady hand game a house encourage them to have more than one room or a doorbell system a lighthouse or some type of toy which produces sound or movement .
encourage learners to use everything that they have learnt about electric circuits and include different components such as switches .
let's say you want to become an electrical engineer or electrician .
one of the things that you will be doing is to design systems that use circuits to solve problems for people whether it is the wiring in a house an alarm bell a lighthouse on the coast or constructing toys which use electrical energy to work .
design brief
you are an electrical engineer and you need to come up with a design for an electrical system to solve a problem .
you need to design and make a system that uses a circuit to produce movement light sound or heat .
write a design brief where you identify what you are going to make and why it needs an electric circuit .
investigate
the next step in the design process is to do some research about the instrument that you are going to make .
you can use books and the internet to do your research .
answer these questions when doing research about your electrical system
how is this system normally made ?
what components does it need ?
what type of energy will be produced from electrical energy ?
why do people need this system ?
what problem does it solve ?
design
now that you know a bit more about the system you want to make you need to design how you are going to make it .
your system has the following specifications
your system has the following constraints
answer these questions
now you need to draw some designs for your system .
use scrap pieces of paper to do your first designs .
once you are happy with your design use the space below to draw your design .
label your drawing showing what materials you are going to use for the different parts .
when you are making your system you might get better ideas to improve the design as you test it out to see if it produces the required output .
so come back afterwards and draw on the bottom half of the page; show what you really decided to make .
make
now make your system !
after you have all finished making your systems perhaps go around and look at what others have done .
ask each other questions to see what you can learn from others .
you will also have to present your project to the class so use this time to get ideas about how to present your idea and product that you made .
evaluate
before we get on to presenting the projects you need to evaluate your own project .
you can then use this evaluation in your presentation to show others what worked and did not work .
does your system look like your initial design ?
does your system produce a movement sound light or heat ?
where would people use the system you designed to solve a problem in our daily lives ?
is there anything you might do differently to improve your design ?
communicate
an engineer needs to be able to present their designs to show others what they have come up and communicate their ideas .
engineers can present a written report and hand in their design drawings .
but often an engineer will need to present the design and project by speaking and giving a verbal report .
your last task in this design project is to present your system to your class .
these are your instructions
each learner must be assessed for the actual system that they built and their designs drawings and planning .
and each learner must be assessed in the way that they present their project orally .
pay special attention to the learner's ability to project their voice and engage with the class their ability to explain what they have done and whether they answered all the questions outlined in the instructions above .
name five things that we would not be able to do without using electricity .
explain why you think each of these things is important to us .
learner dependent answer .
check that they have justified why each is important .
jason builds an electric circuit that includes a bulb and battery for his bedside table so that he can read at night but the bulb does not light up .
list three things that could be wrong .
the battery could be placed the wrong way the battery is flat there is a break in the connection somewhere one of the wires is not connected properly or is broken the bulb may have blown' meaning the filament inside the bulb is broken .
jason does not want the battery in his bedside light to run out of energy .
what could he do ?
he can include a switch to turn it on and off to save the battery .
list three electrical devices that use energy from a battery .
torch cellphone walkman etc .
list three electrical devices that use energy from a mains supply .
microwave stove iron hairdryer fridge etc .
draw an electric circuit diagram for the system that you designed and made in the design project .
this unit lends itself to searching for information pictures simulations and videos on the internet in the library in magazines and books .
the basic information about the main topic is provided here but teachers and learners should explore the topic further .
we are so used to switching on electrical appliances that we hardly think what makes it possible to have these things .
our focus turns to appliances that need a mains electrical supply .
you have listed examples like a television a computer a kettle and many others before .
the big question here is where does mains electricity come from?'
a battery has stored energy which can provide electrical energy .
however our homes schools shops and factories cannot run on batteries because they cannot store or provide large amounts of energy .
we use electricity every day .
the main supplier of electrical energy is from power stations .
coal oil and natural gas are fossil fuels .
some people think that fossil fuels are the remains of dead dinosaurs but this is not true !
actually most of the fossil fuels we find today were formed millions of years before even the first dinosaurs .
fossil fuels were once alive !
do you remember learning about fossils in gr. 5 earth and beyond ?
write down what you think a fossil is .
a fossil is the remains of a dead organism plant or animal from millions of years ago .
so fossil fuels are actually the remains of prehistoric organisms that lived millions of years ago !
different fossil fuels come from different organisms and formed in slightly different ways .
how fossil fuels are made
this activity is meant as a comprehension for reading appreciation .
ideally the learners should read the text themselves and then answer the questions that follow .
the ability to read a lot of text identify the main facts and then answer questions or summarise text is an important skill .
instructions
300 million years ago.. .
think about what the earth must have looked like back then !
there were swamps and marshes everywhere and it was warmer than it is today .
ancient trees ferns and plants grew everywhere .
very weird looking animals roamed the earth and even stranger looking fish lived in the rivers and deep in the oceans and seas .
when these prehistoric plants and animals died their bodies their bodies decomposed just in the same way as organisms decompose today .
the dead organisms became buried under layers and layers of mud rock sand and water .
over time these layers built up and became very deep and they pushed down with a great pressure on the layers below it .
millions of years passed and the dead plants and animals slowly decomposed and formed fossil fuels .
different types of fossil fuels were formed depending on different factors .
for example whether it was the remains of plants or animals or a combination and how long the remains of the organisms had been buried for .
the type of fossil fuels that formed also depended on the temperature and pressure conditions during the decay of the organisms .
oil is a dark thick liquid that can be used to make petrol to burn in vehicles such as cars buses and trucks .
natural gas is colourless and it is used mostly in homes for heating and cooking food .
oil and natural gas formed from organisms plants and animals that lived in the oceans before there were dinosaurs .
when these organisms died they settled on the bottom of the river bed or ocean floor and the layers built up under mud and sand silt .
the mud and sand slowly changed into rock and the rock and water pressure pushed down on the remains of the dead plants and animals .
over millions of years of being under heat and pressure the dead plants and animals changed into a thick liquid called crude oil .
in deeper hotter places tiny bubbles of natural gas formed .
these were trapped under the rocks .
over time some of the oil and natural gas began to work its way up through the rock and to the earth's crust and into rock formations called caprocks' .
today most of the oil and natural gas is collected from these caprocks by drilling down through the layers of rock .
coal is a black rock that can be burnt to produce energy in power stations all over the world .
coal was formed from the dead remains of trees ferns and some other plants that lived 300 to 400 million years ago .
this was when the earth was mostly covered in swampy forests .
these kinds of plants were very different to the plants that we get today .
over time the layer of dead plants at the bottom of swamps was covered with layers of water and mud .
the top layers squashed down on the dead plants .
over millions of years the heat and pressure turned the plants into the coal that we mine today .
the energy in coal originally comes from energy from the sun .
plants on earth used the energy of the sun for photosynthesis and to grow .
this energy was stored in the leaves flowers and stems of the plants .
as the plants died the energy was trapped .
questions
what are the three fossil fuels discussed in the above story .
coal oil and natural gas
the organisms that fossil fuels were formed from lived many years ago and are different to the organisms that we get today .
how many millions of years ago was this ?
300 million years ago
the dead organisms are covered in sediments over time .
do you remember learning about sediments in gr. 5 earth and beyond and how sedimentary rock forms ?
write a description of what sedimentation is .
sedimentation is when particles either sand rock or organic material settle on the bottom of a river or the ocean floor and over time form layers which begin to compact .
what are the two main factors which turned the remains of organisms into fossil fuels deep under the layers of rock and mud ?
high pressure and heat
explain why we say that all our energy originally comes from the sun even in fossil fuels .
the organisms that fossil fuels are made from lived millions of years ago .
the plants used the sun's energy to make food by photosynthesis .
when they died this energy was trapped in the plants' remains which then turned into fossil fuels .
the animals that ate the plants got their energy indirectly from the sun through the plants .
when these tiny animals died the energy was also trapped in their remains which became fossil fuels .
do you remember learning about the states of matter in matter and materials .
each of the three fossil fuels discussed here is a different state of matter .
say what they are .
coal solid oil liquid natural gas gas
the process of coal formation and natural gas and oil formation have similarities but also differences .
draw a table where you compare these two processes .
give your table a heading .
possible answers
a comparison of the process of coal formation and natural gas and oil formation different fossil fuels
fossil fuel formation video
the way we obtain the different fossil fuels is also different .
coal is usually obtained by digging mines into the rock and sand to reach the coal deposits deep under the surface .
this creates a huge hole in the surface of the earth as you can see in the photograph of a mine .
oil and natural gas is obtained by drilling down through the rock .
a hole is sunk with a huge drill so that the oil and natural gas can be reached and then brought up to the surface .
this normally takes place in the ocean as you can see in the oil rig in the photo .
search the internet to find out which countries in the world have large quantities of coal oil and natural gas .
search the internet to find out which three countries in the world use the most fossil fuels .
the main supplier of electricity in south africa is eskom .
let's look at a power station to find out how coal is used to produce electricity .
look at the diagram and the steps which outline the process to make electricity from coal
materials
instructions
the sequence should be something like sun rightarrow plants and animals rightarrow fossil fuels coal rightarrow power station rightarrow electricity rightarrow delivery to home on power lines rightarrow tv or other appliance .
fossil fuels are non renewable resources of energy .
this is because they take millions of years to form .
once these fuels are burnt they cannot be recovered or reused .
they are non renewable .
a learner's conception of millions of years' might not be well grounded .
fossil fuels are not renewable because we use them up far quicker in a few centuries than they can form millions of years .
this point will be lost if learners can not distinguish between hundreds and millions .
this should be addressed by the teacher to focus on meaning of hundreds and millions .
the burning of coal produces billions of tonnes of carbon dioxide each year .
carbon dioxide is one of the greenhouse gases that contributes to global warming .
people on earth are using up these deposits of fossil fuels much much faster than they are being made as they take millions of years to be made !
look at the diagram of a power station again .
do you see the smoke that is given off when the coal is burnt ?
this causes huge environmental concerns as it is polluting our atmosphere .
a bit later in this chapter we will look at other ways of producing energy which unlike fossil fuels are renewable .
do you hear your parents and other adults talk about the cost of living ?
do they remind you to switch off lights and other appliances that are not in use ?
electricity is an expensive resource !
a learner might make the reasonable point that the coal is burnt anyway whether you leave that light on or not .
but the point is to show that cumulatively saving electricity can have an effect on reducing demand on power stations and it also reduces the amount that your individual household spends on electricity if you use it efficiently .
electricity is costly because
when electrical energy enters your home it must pass through a meter .
have you ever seen a white box outside your house ?
this is the electricity meter .
we already mentioned that some electrical appliances use more electricity to run than others .
appliances that heat use the most energy such as a geyser or heater .
how do we know which electrical appliances use more electricity ?
this could be an individual task each learner should look for this information so that they become familiar with looking for ways to save energy .
this is how we find out !
instructions
make the link between the unit w and kw where a kilowatt is 1000 watts .
similarly metre m and centimetre cm and gram g and kilogram kg .
as well as metre and millimetre mm and ampere a and milliampere a .
record all the power values in column 3 in watt .
if the power is given in kw multiply this number by 1000 to get the value in watt w .
for example 2 kw × 1000 2000 w
if the device does not show a value in w or kw look for two quantities given in volt v and milliampere ma .
multiply these two numbers and then divide the answer by 1000 to get the power in watt .
for example 240 v × 150 ma 36 000 w
36 000 ÷ 1000 36 w
you divide by 1000 to correct for using ma instead of a .
power w voltage v ÷ current a
teacher note the values in the table are not exact but the order of magnitude should be similar .
now arrange the appliances in the next table in terms of the power required .
the list should be from small to large values of the power .
questions
what do you see in this table ?
which two appliances have the lowest power requirements ?
what do these appliances have in common ?
possibly the cellphone charger and energy saving bulb .
they are small and only require a small amount of energy to work .
the bulb is built specifically to use less energy .
which two appliances have the highest power requirements ?
what do these appliances have in common ?
possibly the kettle and iron or any other heating device they are used to produce heat which uses a lot of electrical energy .
electricity is expensive so we should try and save electricity .
this is not the only reason to try save electricity .
remember when we spoke about the pollution given off by coal power stations ?
why else do you think it is important to try save energy and reduce your power usage ?
the burning of coal in power stations produces carbon dioxide a greenhouse gas which contributes to global warming .
if enough people reduce electricity usage in their homes this will reduce the demand on coal power stations meaning they have to burn less coal which will in turn have less of an environmental impact .
there are many different ways to save electricity from small actions to larger actions such as using renewable energy resources .
we will discuss this a bit later in the chapter .
how can you prevent wastage of electricity in your home ?
name four possible ways .
use energy saving light bulbs install a solar water heater switch off all electrical devices that are not in use and use as little hot water as possible .
we discussed a world without electricity and we all realised how dependent we are on this resource .
it is illegal for anyone to use electricity that was generated by eskom without their permission .
some people make illegal connections because they don't want to pay for the electricity .
they cut through the insulation in a power line and attach other cables to this line .
they can then direct some electricity to their house or workplace .
these connections are dangerous to people as they are often unsafe .
people who make illegal connections try to get electricity for free but the dangers are not worth it .
it is not worth your life !
accidents caused by electricity happen all the time .
people often get hurt or even killed by electricity because they do not use it safely .
not only is it important to know how to use electricity safely but also what to do if someone is hurt or shocked by electricity .
what types of emergencies can happen at home or at school with electricity ?
someone could get a shock on a plug or exposed wire someone could put an electrical appliance in or near water and get a shock there could be a power outage and when someone is trying to fix the problem they could get shocked etc
find out about the emergency services in your area and write down their names and telephone numbers .
also write this information on a piece of paper and stick it to the wall next to your phone or in a central place in your home .
consider inviting an electrician to talk about electricity and safety to the class .
accidents with electricity can be avoided .
we just need to be smart about working with electricity .
let's formulate some safety rules for working with electricity .
this was done in gr. 5 but it is a good idea to revise it again as electrical accidents often happen in the home and at school .
instructions
electricity does not flow .
electric current flows .
questions
the person in the illustration above is using a table knife to remove a coin that has fallen in the toaster before switching off the appliance .
what are the dangers related to this act ?
the person can get shocked as electricity can pass from the toaster through the metal knife and through the person .
what safety rule can you formulate regarding this ?
first turn the toaster off and unplug it and use a wooden or plastic knife .
what could be done to the cable to make it safe to use ?
replace the cord or else wrap insulation tape around the broken cord .
however this will not prevent a short if the wires inside also have perished insulation .
it is best to replace the cord .
what safety rule can you formulate regarding this ?
never use an appliance that has a broken cord or has some of the metal wire showing through the cord casing .
why is it dangerous to pull the boy from the electric wire ?
electric current can flow from one person to the next so you will also get shocked .
what can the helper do to save the boy without being shocked by the electricity ?
use a non plastic non metal object to separate them from the electrical source .
what safety rule can you formulate regarding this ?
never try to pull someone who is being shocked away from the appliance .
why is this not a safe place to play ?
high voltage fences can shock you even if you stand near them without actually touching them or you might accidentally bump against the fence .
what safety rule can you formulate regarding this ?
never play near to or on electric fences or power lines .
why is this connection dangerous ?
too much electric current flowing to one plug is dangerous .
one multi plug adapter is safe but do not put adapters into each other .
rather use 2 different plug points .
teacher's note the real danger is that overloading the plug causes heating of the circuit which can result in fire .
what safety rule can you formulate regarding this ?
never put too many appliances into one socket .
why is it dangerous for the children to play outside during the lightning storm ?
if this powerful natural electricity strikes close to you it will try to get to the ground through you .
our bodies are good conductors of electricity .
why should no one play under a tree when it is storming ?
the lightning is attracted to high points such as a tree and can shock the tree and also kill anyone underneath it .
explain why it is not a good idea to be swimming when there is lightning in the sky ?
lightning could strike the water .
water with dissolved substances such as salt or chlorine is a good conductor of electricity and you can get shocked and possibly die if you are swimming .
what safety rules can you formulate regarding lightning ?
do not play outside when there is thunder and lightning .
why is the gardener unsafe when mowing the lawn in the rain ?
give at least two reasons .
water is able to conduct electricity so you can get a shock if you are touching an appliance and water drips into the socket cord or motor .
secondly he is not wearing shoes which is dangerous as he could cut himself and the current can flow through him and into the earth .
what safety rules can you formulate regarding using electrical appliances outside in the garden ?
never use electrical appliances outdoors in wet weather or if you are wet .
wear shoes when using electrical appliances .
we have seen above that fossil fuels are non renewable resources of energy .
what do you understand by the word non renewable' ?
this means it cannot be renewed reused .
there is a finite supply which will be used up one day .
so if we are using an energy resource which is non renewable then this will be a problem in the future when these resources run out .
are there other sources of energy ?
scientists and engineers are looking for ways to harness energy from renewable resources .
a renewable resource is the opposite to a non renewable resource .
it will not run out and can be used over .
renewable energy sources include natural phenomena such as sunlight wind tides and plant growth .
the energy comes from natural processes that happen over and over .
renewable energy video
why do you think natural phenomena such as sunlight and wind can be considered as renewable ?
this is because the sunlight and the wind will not run out' .
this is another place to speak of orders of magnitude .
these resources are available so long as the solar system lasts in its current form roughly 3.5 billion years they say .
so these are renewable because they will always be available to us as a species even if we last a few million years more having only really been around about 150 000 years or so .
examples of renewable energy resources are
sun wind and water can be used as sources of energy .
solar panels can be fitted to houses but this source of renewable energy works best on sunny days and is less effective on cloudy days .
wind energy can be collected with a windmill or wind turbine which can be big and noisy .
hydroelectric power stations harness the energy in water stored in high dams .
it is only possible in areas where there are high mountains and rivers .
solar panels which convert the sunlight energy to produce electrical energy are also called photovoltaics .
there are also solar water heaters but this is a different system to solar panels .
solar heaters directly heat water .
wind energy video
the first windmills were developed in persia in about 600 b.c .
but the first windmill to produce electricity was in denmark in 1890 .
south africa also has large reserves of uranium which are used in the koeberg nuclear power station .
learning how to debate is an important skill .
after doing this activity you could practise debating skills in the class by getting two groups to discuss opposing sides of the story .
each group must understand that they have to justify an argument for each side of the debate .
what are the advantages and disadvantages of renewable and non renewable sources ?
there is a lot of debate around the use of renewable and non renewable sources for energy .
let's join this debate !
instructions
how hydroelectricity works video
if time permits learners can do a mini research project on one of the renewable energy resources and present a poster in which they answer questions such as how is this renewable energy resource harvested and used to produce electricity?' is this resource used in south africa?' etc .
these can be stuck up as posters in the classroom for others in the class to read and learn from .
the sun produces energy which plants capture and use to make food through the process of photosynthesis .
animals eat the plants .
when these prehistoric plants and animals died millions of years ago their remains were turned into fossil fuels such as coal oil and natural gas over a long time .
this was due to being covered in layers of sediment of mud and water which over time turned into rock and exerted a great pressure and heat on the remains .
today these fossil fuels are mined and collected from inside the earth's crust .
oil is processed to make petrol and diesel and the energy from the fossil fuels is used for example in cars where it is burnt and the energy released powers the cars .
why are fossil fuels considered non renewable resources ?
this is because there is a limited supply of fossil fuels which will run out one day as we are using fossil fuels faster than they are made which takes millions of years .
they cannot be reused .
write a paragraph in which you explain why you think humans should investigate alternative energy sources such as renewable energy sources and how this might help the earth .
learner dependent answer but assess whether learner has the ability to present an argument and justify their reasoning .
one of the reasons which learners could present includes the fact that our reliance on non renewable energy resources is not sustainable and poses a problem for the future if they run out .
furthermore burning fossil fuels has a severe environmental impact as the carbon dioxide released contributes to greenhouse gases and global warming .
what type of electrical appliances in our homes use the most energy in a specific time ?
this depends on the activity and usage but the most energy will probably be used by heating devices such as a geyser or heater .
imagine that you are writing an article for your local newspaper on how to save electricity in your homes .
use your imagination to write your article telling people how to save electricity .
use the space below .
give your article a catchy heading .
assess learner's ability to write creatively about a science related topic .
they are required to use the knowledge they have learnt in this chapter to write something creative .
tips to save electricity could be turning off lights when not in the room using energy saving lights reducing shower time to use less hot water turning off the geyser during the day using a gas stove instead of electrical stove and bigger actions such as installing solar power etc .
how do you think saving electricity will reduce the demand on eskom's power stations ?
the more electricity you use the more coal needs to be burned at the power stations to produce electricity .
saving electricity means that you use less electricity so there is less demand on the power stations .
what is an illegal electrical connection ?
how do you think the local government could stop or reduce the amount of illegal connections ?
an illegal connection is when someone accesses electricity by cutting a power line and attaching another line and then not paying for it .
the local government could try stop this by firstly trying to supply the poorer areas with appropriate electricity access points going around and checking that there are not any dangerous connections raising awareness about the dangers of illegal connections through advertising boards on radio in the newspaper etc .
assess any other viable answers that the learner may come up with .