Machines

ELATE PHYSICS

UNIT 3

TOPIC : Machines

SUBTOPIC : Efficiency of machines

CLASS : Senior Three

NUMBER OF LEARNERS: 50

DURATION: 120 minutes minimum – 240minutes maximum

INTRODUCTION:

Learners must have been introduced to machines and covered the following subtopics; Work, Energy Power, Force (effort, load), Mechanical Advantage (MA) and Velocity Ratio (VR).

Machines are devices that make work easier though not smaller. This is achieved by the application of a force (effort) at one point in order to overcome another (load) at another point.

People and machines cannot do work without a supply of energy. We get energy from the food that we eat. Machines are fed with energy in many other forms e.g. fuels such as coal, oil and gas, solar energy, hydro electricity, nuclear energy etc.

A machine converts the energy supplied into another form. The total amount of energy input the machine is equal to the total amount of energy output. This implies that a machine doesn’t consume energy; however the useful energy or work done is usually less than the total energy input.

The amount of time taken to do a piece of work may vary from machine to machine depending on how powerful the machine is. A faster machine uses more power in doing a piece of work.

ACTIVITY 1:

The teacher will guide the class in reviewing the previously taught areas that relate to machines. Review the following;

• Work, Energy, Power, Force, MA and VR.
• Examples of simple machines
  • Levers
  • Pulleys
  • Inclined plane
  • Hydraulic machine
  • Petro engines.

ACTIVITY 2:

The teacher organizes the class into groups of 5 to 10. Each group will carry out the following assignments.

Record examples of commonly used machines in the following categories;

1. Levers

Machine	Note where the pivot is found	Identify the class of lever
Wheel barrow
Human fore arm
Bottle Opener
Pair of Scissors
Pair of pliers

2. Pulleys

Draw diagrams to show the following pulley systems

• Single fixed
• Single moving
• Block and tackle system of VR=4

3. The inclined plane. A slope or ramp which allows a load to be raised more gradually and by using a smaller force (effort) than if it was lifted vertically upwards.

As we climb up a stair case we use the principle of the inclined plane.

h

Find the formula for the work input and the useful work output.

ACTIVITY 3:

Efficiency = =××100%

=MA××100%

PRACTICAL EXERCISE OF MEASURING THE MA AND EFFICINCY OF A BLOCK AND TACKLE PULLEY SYSTEM AND SHOWING THE VARIATION OF MA WITH LOAD AND EFFICIENCY WITH LOAD

INSTRUCTIONS

1. Assemble the block and tackle system as shown in the diagram above.
2. Suspend known masses between 1.0kg to 6.0kg on the system in turn and record readings of the spring balance for the effort needed to just raise the loads.
3. Work out the MA and efficiency for each load.
4. Record your readings in the table below.

Mass/kg	Load/N	Effort/N	MA=Load/effort	Efficiency
1.0
2.0
3.0
4.0
5.0
6.0

5. Plot graphs of MA against load and efficiency against load.
6. What deductions can you make from the graphs?

ACTIVITY 4

Mr. Kapere is not keen at taking his car for service when the mileage is due. He has always reasoned that “after all the car still moves perfectly well.” In a small note to kapere, advise him as a friend on the disadvantages of continual use of the car without servicing it.

• List down as many causes of inefficiency in machines and state how they can be minimized.
• Prepare a group’s presentation to the whole class.

• inary level Physics by AF Abbott

PHYSICS

SAMPLE LESSON PLAN

DATE	CLASS	SUBJECT	NO.OF LEARNERS	DURATION	TIME
…./…./…	SENIOR THREE	PHYSICS	50	80 MINS	8.00 – 9.20am

Topic: Machines

Subtopic: Efficiency

Time: 80 minutes

Objectives: by the end of this lesson, learners should be able to:

• Define work input, work output, velocity ratio, mechanical advantage and efficiency.
• Derive the relationship between Efficiency, velocity ratio and mechanical advantage.
• Identify the causes of inefficiency in a simple machine such as a pulley system.

Teaching aids:

• Pulleys and pulley strings
• Loads (masses of 100g)
• Inclined plane
• Spring balance

References:

• The world of Physics by John Avison
• Ordinary level Physics by AF Abbott

Time/Minutes	Teacher’s activity	Learners’ activity	Comments
10	Introduces lesson by defining work, energy and power. Finds out what Learners know about work and different types of energy.	Suggest different forms of energy and its transformations from one form to another.
20	Introduces mechanical advantage as the ratio of load to effort Velocity ratio as the ratio of distance moved by effort to that moved by load in the same time. Simple illustrations in form of calculations	May ask questions for clarity Try out the numeric questions given by teacher
15	Shows class how simple pulleys of different velocity ratios may be assembled (demonstration) Asks learners for any observations and conclusions made Responds to learners’ queries.	Make observations and draw conclusions Reactions Make notes
35	The inclined plane. Use of spring balance to find effort that pulls load up the incline. Organizes class into groups and provides necessary apparatus for inclined plane.	Measurement of effort, load, distance by effort and distance covered by load. Calculation of Work input, work output and efficiency for different loads. (group work) Relationship between efficiency and load(graph) Relationship between MA and load.
5	Supplements learners’ observation and conclusions Concludes lesson.

Lesson Evaluation:

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Heat Transfer

TEACHERS’ GUIDE

SUBJECT : PHYSICS

TOPIC : HEAT

SUB-TOPIC : Heat transfer

CLASS : Senior One

CLASS SIZE : 60 Students

TIME REQUIRED : Minimum: 240-360 minutes

Brief description of the unit

This unit discusses the types of heat transfer, the factors that affect the rate of heat transfer as well as applications of heat transfer. Heat is a form of energy that produces a sensation of warmth when absorbed by our bodies. Heat energy is the commonest form of energy in applications by humans and other living things. Heat energy is used for preparing food, keeping us warm, drying clothes, etc. Almost all forms of energy finally degrade to heat.

Unlike electricity, heat energy leaks easily. There is therefore need to study the ways heat energy is transferred with the aim of conserving it, using it economically so as to reduce global warming.

Main Content to emphasise

Heat transfer by conduction, convection and radiation.

Objectives

By the end of the topic, the learners should be able to:

1. Define thermal conduction, convection and radiation.
2. Arrange Iron, copper, Aluminium and glass in order of their thermal conductivities.
3. Describe the mechanism of thermal conduction in terms of the simple kinetic theory.
4. Explain the applications of good and poor conductors of heat.
5. Illustrate the process of thermal radiation.
6. Discuss the factors that determine the rate of thermal radiation.
7. Demonstrate practical applications of good and poor thermal radiators.
8. Explain the process of thermal convection.
9. Describe practical applications of thermal convection.
10. Identify situations where energy can be conserved through good usage of factors affecting thermal transfer.
11. Compare the efficiency of different types of charcoal stoves with reference to heat transfer.

Methods

Group work

The class should be divided into groups of 5 – 10 with each group having a secretary and a chairperson.

Teaching / learning aids

Source of heat and tripod stand; Iron, copper, aluminium and glass rods of the same length and diameter; Wax; Stop clock

Job related life skills

In forming the groups and during the activities, ensure that the following job-related life skills are deliberately achieved.

• Personal attributes: - behave appropriately, punctuality, reliability, self confidence, seek advice, show tenacity and motivation, be analytical and imaginative.
• Communication: - ability to read, write, listen, and speak in appropriate ways for different audiences. Know and apply general and specialized vocabulary.
• Team work: - ability to cooperate and share tasks with colleagues.
• Problem solving: - goal focused, seek out relevant information, identify constraints, evaluate alternatives and make decisions/ choices.
• Implementation and application: - the ability to carry out complex operations and follow instructions to achieve accurate results.
• Application of number: - ability to work with and present numerical data, using appropriate intermediate calculations.
• Information skills: - ability to present evidence to meet the needs of different audiences using graphs, reports and images.

Activity one

Comparing the rates of heat transfer by conduction in different materials.

Ask the learners should do the following:

• Place one end of each rod in the flame of a candle or a Bunsen burner, while holding the other end.
• Describe the mechanism by which heat travels along the rod to their hands.
• Measure and record the length of time it takes the heat to reach their hands through the rod.
• Describe a better way of comparing the rates of thermal conduction of the different materials, using the apparatus given or any other that is available.
• Carry out the experiment and arrange the materials in order of their conductivities by attaching three pieces of wax at equal intervals on each rod and then simultaneously heating the ends of the rods in a flame.

	Time taken for the 1st piece of wax to fall off	Time taken for the 2nd piece of wax to fall off	Time taken for the 3rd piece of wax to fall off	Ranking in order conductivity(best No. 1)
Copper
Iron
Aluminium
Glass

NB

The rods should be long enough to get measurable time differences.

Ask the learners to discuss the applications of good conductors and poor conductors.

Activity Two

Heat transfer by convection.

Round bottom flask, heat source, potassium permanganate, glass tube.

Ask the learners to do the following;

• Fill the flask with water and carefully drop grains of potassium permanganate at the bottom of the flask using the glass tube.
• Apply a gentle flame at the bottom of the flask and observe.
• Describe and explain the observations.
• Discuss how convection takes place in gases.
• Discuss how convection is applied in house ventilation. Explain the value of good ventilation to comfortable living.

Activity Three

Heat transfer by radiation.

Teaching / learning aids

Hot water, cubic metal container, or Leslie cube, thermometers, kitchen foil, source of heat (radiant coil, filament bulb, or candle).

Ask the learners to do the following;

• Place their hands at a safe distance above, below and at the side of a source of radiant heat and describe the mechanism by which heat reaches their hands in each of the positions.
• Fill the metal cube with hot water and feel the heat at a distance from each side of the cube.
• Describe and explain the difference in the amount of heat felt on each side of the cube.
• Suggest better ways of comparing the rates of thermal radiation from the different surfaces.
• Carry out an experiment to compare the rate of radiation of heat by different surfaces.

One possible experiment is by holding a thermometer with a blackened bulb (placed centrally) at distance from a surface of the Leslie cube containing hot water and recording the temperature readings at regular time intervals. This is repeated for the different types of surfaces of the cube.

	Temperature in oC recorded by thermometer at 30 second intervals
	30	60	90	120	150	180	210	240	270	300
Dull surface side of the cube
Shiny surface side of the cube
White surface side of the cube
Black surface side of the cube

Plot the graph of temperature against time for the different surfaces on the same axes. Use computer spreadsheets where possible.

Comment on the graphs.

1. Discuss the type of finishing you would recommend for each of the following:

a. The inside walls of a bedroom of a house in a hot area.

b. The outside wall surface of a house in a hot area.

c. The inside walls of a bedroom of a house in a cold area.

d. The wall surface of a house in a cold area.

2. Discuss the economic implications of the choice of colours when finishing a house.

Experiment on rates of absorption of heat.

Learners are given a shiny polished pan with a cover that has a hole for a thermometer and a similar pan that is all blackened. The two pans are put out in the hot sun. Temperatures of the water are taken every minute for ten minutes.

The results are recorded in a table.

	Temperature in oC recorded by thermometer at time intervals in minutes
	1	2	3	4	5	6	7	8	9	10
Dull surface pan
Shiny surface pan

Plot the graph of temperature against time for the two surfaces on the same axes. Use computer spreadsheets where possible.

Comment on the graphs.

The learners should discuss the applications of good / poor radiators and absorbers in the home, in dressing, in vehicles, etc.

With reference to conservation of energy, the learners describe one situation where it is necessary to reduce the rate of heat transfer so that energy is conserved (economised).

With reference to conservation of energy the learners describe a situation where it is necessary to enhance the rate of heat transfer so as to conserve (economise) energy.

Activity Four

1. Groups should carry out a project on one of the following

• Keeping cooked food warm for a long time using local materials.
• Firing bricks more effectively.
• An energy saving charcoal stove.

2. The groups present their essays to the class.

Links

http://en.wikipedia.org/wiki/Thermal_radiation

http://en.wikipedia.org/wiki/Solar_hot_water

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm

Requests

Pictures of a vacuum flask, green house, domestic solar water heater.

Exercise

1. Describe an experiment to show that black surfaces are better absorbers of heat than shiny surfaces.

2. The diagram below shows two cubes of the same dimensions A is black while B is shiny. The cubes are both filled with cold water. A source of heat is placed mid-way between the cubes.

Explain what is observed on the thermometers.

3. Explain why the sea remains cooler during day and warmer during night.

4. State any two factors on which the rate of heat transfer along the length of a metal bar depends.

5. Distinguish between conduction and convection.

6. Distinguish between convection and radiation.

7. What factors affect the rate of heat radiation from a surface?

8. Explain how convection determines ventilation of a house.

9. Use the kinetic theory of matter to distinguish between poor conductors and good conductors of heat.

Scheme of work

Sub-topic	Periods	Specific objectives	Content	Teaching and learning strategies	Notes
Conduction	6	Define conduction. List the factors affecting the rate of conduction. Carry out experiments to compare good and bad conductors. Carry out experiments to show that water is a poor conductor of heat. Explain applications of conduction.	Concept of conduction. Factors affecting the rate of conduction in solids. Compare conductors and insulators. Water as a poor conductor of heat. Applications of conduction.	Learners carry out experiments to compare good and bad conductors. Discuss applications of good and bad conductors	Application treated qualitatively eg vacuum flask, flat iron and insulation. Rate of conduction treated qualitatively using simple experiments.
Convection	6	Define convection. Describe how convection current is formed. Experimentally demonstrate convection current. Describe applications of convection.	Concept of convection. The convection current. Applications of convection	Experiments to show convection.	Applications eg in the domestic hot water system, land and sea breezes, ventilation and car radiators.
Radiation	7	Define radiation. Carry out experiments to compare radiators and absorbers. Explain the application of radiation of heat. Describe how solar energy can be trapped and used in a water heating system.	Concept of radiation. Factors affecting radiation (or absorption). Comparing radiators(emitters) and absorbers. Application of radiation. Green house effect. Solar heating system.	Experiments with good and bad absorber (or radiators). Discuss how conduction, convection and radiation considerations are applied in the vacuum flask.	Effect of nature of surface on absorption and emission of radiation.

Sample lesson plan

Class: Senior one.

Subject: Physics

Topic: heat.

Sub topic: transfer by conduction.

Time: 80min

Number of learners: 40 - 80

Objectives: to define conduction, carry out experiments to compare good and poor conductors.

Method:

Group Work and experiments

Teaching aids:

Source of heat and tripod stand; Iron, copper, Aluminium and glass rods of the same length and diameter; Wax; Stop clock.

Time	Theme	Teachers activity	Learners’ activity
5min	Review	Review work done on temperature and thermometers	Answer question on temperature and thermometers.
15min	Rates of thermal conduction.	Provide apparatus and give instructions for experiment to compare rates of conduction	Carry out experiment to compare rates of conduction.
20min	“	Guide learners to present results and discuss them.	Present their results to class and class discusses the results
15min	Applications of thermal conduction	Gives instructions and supervises.	Discuss applications of conduction in groups
20min	“	Guides the discussions	Present results of their discussions of applications of conduction to the class.
5min	“	Give assignment on domestic applications of conduction.	Take assignment.

Exercises:

1. Describe an experiment to show that black surfaces are better absorbers of heat than shiny surfaces.

2. The diagram below shows two cubes of the same dimensions A is black while B is shiny. The cubes are both filled with cold water. A source of heat is placed mid-way between the cubes.

Describe and explain what is observed on the thermometers.

3. Explain why the sea remains cooler during day and warmer during night.

4. State any two factors on which the rate of heat transfer along the length of a metal bar depends.

5. Distinguish between conduction and convection.

6. Distinguish between convection and radiation.

7. What factors affect the rate of heat radiation from a surface?

8. Explain how convection helps in ventilation of a house.

9. Use the kinetic theory of matter to distinguish between poor conductors and good conductors of heat.

Electricity

TEACHER’S GUIDE

SUBJECT : PHYSICS

TOPIC : ELECTRICITY

SUBTOPIC : DOMESTIC ELECTRICITY ENERGY CONSUMPTION

CLASS : SENIOR FOUR

TIME REQUIRED : MINIMUM 240 MINUTES, MAXIMUM 360 MINUTES

Brief description

This unit deals with safe and economical ways of using electricity in our homes. It explores both domestic and energy consumption and how through understanding how electric energy is generated during domestic use money can be saved.

Electrical energy is the most environmentally friendly form of energy, as no green house gases or pollutants are emitted during its use. Increased use of electricity would save/reduce the destruction of forests and its negative impact on the environment. However, the electrical energy produced is limited hence leading to high-energy bills, which in many cases are difficult to understand by many customers.

As such, there is need to sensitise the electricity energy users on how to save on the energy used by the household. At the same time those who are not currently using electricity should be enabled to use it. It is hoped that the learners should be able to interpret energy bills and advocate prudent energy usage in their homes and channel savings to other development needs.

Objectives

By the end of these activities the learners should be able to:

1. Read an electricity bill and establish its authenticity, owner, and time frame.
2. Interpret correctly the terms used in the bill
3. Calculate correctly the payment arrived at in the bill.
4. Read and interpret correctly the rating written on an electrical appliance.
5. Estimate energy consumed by an electrical appliance in a period of time.
6. Suggest ways of economical energy consumption in the home with the aim of reducing energy bills.

Teaching / learning aids

• Energy savers
• Filament bulbs
• Power source
• Electricity bills

Methodology

Group work

Demonstration

Discussion

Job- related life skills

In forming the groups ensure that the following skills are deliberately achieved.

Personal attributes - interpersonal, relationship, persuasion, leadership and creativity.

Communication – communication.

Team working - team work.

Problem solving – analysis.

Application of Number – numeracy.

Information skills – observation

CONTENT

Electricity and Energy Usage in the home

Activity One

Procedure

1. Give the learners a 100W filament bulb.
2. Ask them to describe markings on the bulb.
3. Ask them to calculate the energy used by the bulb when it works for 10hours in joules and then in kWh.
4. Ask one of the learners to demonstrate on the chalkboard how s/he has calculated kWh.

Activity Two

1. Divide the learners in into groups of 4-8 and ask them to discuss the definition of the kilowatt-hour.
2. Encourage participation of all learners.
3. Monitor / supervise the discussions and make the clarification as needed /appropriate.
4. Recap the key ideas with the whole class.

Activity Three

In their groups ask the learners to study the energy bill provided and describe the following;

1. Features that show that the bill is genuine.
2. Features that identify the owner.
3. Features that give the time frame of the bill.
4. The meter readings taken.
5. How the bill is calculated.

Ask the group to make a record of their findings.

Activity Four

Ask the learners to study the marking on the energy saver and filament bulb given and do the following:

1. Explain the meaning of 75W, 240V and 12W, 240V.
2. Find out which of the bulbs costs more.
3. Find out which of the bulbs lasts longer.
4. Learners connect the bulbs to power source and observe brightness and feel the heat given out by each and record their findings.

Activity Five

Give the following activity to your students

The table below gives the appliance usage of households A and B

Household A	Household B
5 energy saver bulbs each 12W used 4hours a day	5 filament bulbs each 75W used 3hours a day

If the standard service charge is sh. 2000 per month, the cost of a unit is Shs. 426 and V.A.T is 18%.

1. Find the amount paid by each household at the end of the month.
2. Advise the household which spends more on electricity on how to minimise the cost.
3. Present your findings to the class.
4. Calculate the saving of household A in a year and suggest the investment that can be made out of the saving.
5. Mention other energy sources used in the household and discuss how they should be used economically.
6. Write an essay outlining the good and bad habits of electricity usage in the house.

Activity Six

1. State the advantages and disadvantages of parallel and series wiring.
2. Identify the three pins of a plug.
3. Wire the plug.
4. Mention and practice safety precautions.
5. Demonstrate the proper position of fuses and switches.
6. Calculate the cost of electrical energy.
7. Calculate the appropriate fuse rating for an appliance.
8. Mention ways of minimising energy wastage.

Activity Seven

Use the following teaching aids to carry out this activity

Teaching/learning aids

• Electric meter.
• Energy savers of different ratings.
• Filament bulbs.
• Electric flat irons.
• Radio/TV.
• Fridge.
• Telephone charger.
• Electric cooker.

Procedure

1. Divide the learners into groups of 5 to 10 members and give them the appliances in the table below then ask them to answer the following questions.

Appliance	Safety provision	Power rating	Speed of meter (very fast, fast, slow, very slow)	Deductions
Energy saver bulb
Filament bulb
Flat iron
Radio
Electric cooker
Electric kettle
Telephone charger

1. Identify and record the power rating of each appliance.
2. Identity any safety precaution provision on the appliance.
3. Connect each appliance in turn to the power source and make observations on the meter.

2. Give a chance to each group to present their findings to the class.

Follow up questions

1. (a) Discuss the factors that may lead to high energy consumption in the household.

(b) For each factor mentioned in (a) give ways of minimising the energy consumption.

2. Describe how each of the safety provisions identified reduces risks of using electricity in the household.

Website Links

http://en.wikipedia.org/wiki/Watt-hour

http://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci797759,00.html

SAMPLE SCHEME OF WORK

TEACHER’S NAME SUBJECT NO. OF LEARNERS

SCHOOL NAME CLASS

WEEK	PERIODS	TOPIC	SUBTOPIC	SPECIFIC OBJECTIVES	CONTENT	METHODOLOGY	TEACHING AIDS	COMMENT
	5	Electricity	Domestic electricity	The learner should be able to: Describe the advantages and disadvantages of series and parallel connections Mention and practice safety precautions when wiring a house Explain the necessity of earthing some electrical appliances Demonstrate the proper position of fuses and switches Calculate the appropriate rating of fuses Calculate the cost of electrical energy consumption using the kWh as the base unit State the advantages and disadvantages of different types of lamps	- Wiring a building - 3 pin plugs - Safety precautions - Cost of electrical energy – the kWh - Lamps (filament, fluorescent, discharge, energy savers)	Discussion Group work Demonstration	- Electric meter - Energy savers of different ratings - Filament bulbs - Electric flat irons - Radio/TV - Fridge - Telephone charger - Electric cooker - tester
	2	Electricity	Distribution of electrical energy	The learners should be able to: Explain how electrical energy is transmitted over long distances State advantages of transmitting power at high voltages	- The grid system for single phase - Advantages of high voltage transmission for long distances	Demonstration Discussion

SAMPLE LESSON PLAN

DATE	CLASS	SUBJECT	NO.OF STUDENTS	DURATION	TIME
…../…./…..	SENIOR FOUR	PHYSICS	40-80	80 MINS	8.00-9.20 am

TOPIC : Electricity

SUBP-TOPIC : Domestic electricity energy consumption

Objectives

By the end of this activity the learners should be able to:

1. Read an electricity bill and establish its authenticity, owner, and time frame.
2. Interpret the terms used in the bill correctly.
3. Calculate the payment arrived at in the bill correctly.
4. Read and interpret the rating written on an electrical appliance correctly.
5. Estimate the energy consumed by an electrical appliance in a given period of time.
6. Suggest ways of economical energy consumption in the home with the aim of reducing energy bills.

Method

Group Work

Teaching aids

• Copies of electricity energy bills.
• A 75W, 240V filament bulbs, an 18W, 240V energy saver bulbs, a 40W, 240V fluorescent tubes, a 1600W, 240V flat irons, a 2KW, 240V kettles.

Time	Content	Teacher’s activity	Students’ activity
5min	Review calculation of electrical power and energy. P = v2/R= VI = I2R Energy = Power x time	Asks students to define electrical power and energy in terms of electrical quantities	Define electrical power and energy in terms of electrical quantities.
5min	The kilowatt hour. Definition The kilowatt hour is the energy consumed by a device of power 1000Watts in 1hour.	Guides students to define the Kilowatt hour as the electricity board unit.	Define the Kilowatt hour.
15min	The energy bill Features of an energy bill: Authenticity The owner The time frame Meter readings Stages of arriving at the bill	Organises students into groups of 5-10 learners. Gives the students the electricity bill copies Asks them to study the bill and describe its features.	Get into groups Receive bill Study the bill and describe its features
10min	Comparison of the energy saver and the filament bulb.	Gives the groups one filament bulb of 75W, 240V and one energy saver bulb of 12W, 240V. Instructs the different groups to explain the meaning of the ratings.	Explain the meaning of 75W, 240V and 12W, 240V. Explain the meaning of the rating.
10min	Differences between the two bulbs. The 12W energy saver gives more light and less heat. The filament bulb gives out less light but a lot of heat. The energy saver is more efficient in lighting and durable although more expensive.	Instructs students to discuss observations made on the bulbs when they working. Listens to the students as they discuss the cost and durability of each of the bulbs	Discuss their observations.
10min	Energy consumed by an appliance and the cost	Asks students to find the difference in the cost of electricity which a house using 5 filament bulbs for 4 hours a day for a month, compared to a house which uses 5 energy saver bulbs for 3 hours a day. Explains to the learners the meaning of: V.A.T and service fee.	Calculate the total energy and the total cost in each case and find the difference in the bills. Listen
20min	Electrical appliances in the home	Instructs learners to present their group findings to the rest of the class and guides in summarising	Each group presents to the rest of the class
5 min	Home work	Gives the learners an assignment	Take note of the assignment.

Lesson Evaluation

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