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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