Unit 8 – Energy Use At Home
STUDENTS’ GUIDE
CHALLENGE
How can a family reduce the amount of electrical energy they use at home? What are
the TRADEOFFS involved in using FLUORESCENT instead of INCANDESCENT
bulbs.
SAFETY NOTE
General classroom safety precautions apply.
PROCEDURE
1. Using the “Energy Savings at Home” Chart below, select and record in your
notebook the ways you choose to reduce by one hour the use of each of the listed
appliances that you have at home.
“Energy Savings at Home” Chart
Reduce Appliance Use
Annual Savings
(By 1 hour a day)
(Dollars)
1HP Air-conditioner (6 months)
$194
Heater (3 months)
$166
Television (per set)
$46
Stereo Amplifier-Speaker System
$33
Incandescent Lamp 100-watts
$33
Compact Fluorescent Lamp 18-watts
$6
Personal Computer
$44
Halogen Lamp
$16
DEHUMIDIFIER 24-liters
$99
Air Purifier 40-100 CFM
$14
Way to Accomplish
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Unit 8 – Energy Use At Home
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2. Reading: “A Cool Energy Decision”
We all use a lot of light bulbs, but few people think much about them. When one
bulb burns out, you tend to replace it with the same kind of bulb. That’s probably
the last time you think about light bulbs until the next time one burns out. This
reading is about whether you should use an incandescent or compact fluorescent
bulb to replace a burned out light bulb? Read on and then decide.
[Diagram 8.1 Compact Fluorescence Bulb] [Diagram 8.2 Incandescent Bulb]
A light bulb often used in our homes is called an incandescent bulb. One of its
problems: it is very inefficient. The typical incandescent light bulb produces as
much as 90% THERMAL or heat energy and only 10% light. That means the bulb
uses a lot of electricity to heat the room rather than to provide light. A second
problem is related to the fact that the bulb produces light by heating up a filament
(thin wire) inside. This filament is actually burning, and when it burns up and
breaks, the light bulb goes out! As the bulb produces light by heating the
FILAMENT, so that it glows very brightly, incandescent light bulbs don’t last very
long.
Compact fluorescent lamps, however, produce light in a different way. The
electricity adds energy to the mercury in the tube (scientists call this “exciting the
gas”). The mercury vapour then releases energy, which hits a special coating called
phosphours. This phosphour coating is spread all along the inside of the tube and
converts the energy to visible light. There is no filament and no burning. This type
of light bulb creates a lot less heat energy and lasts much longer.
Note: Your teacher will help you complete a table in your science notebook like the
one shown here that compares incandescent and compact fluorescent light bulbs.
Based on the information in the table, find the total expense for using each type of
bulb. Add together the cost of the bulb(s) and the cost of the electricity.
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Unit 8 – Energy Use At Home
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Comparison: Incandescent and Compact Fluorescent Bulbs
Type of Light Bulb
Incandescent
Fluorescent
Average Lifetime (hrs)
750
7500
Number Needed
10
1
(For 7500 hr of light)
Total Cost of Bulb(s)
65.00
25.00
Power Rating of Bulbs
100 watts
18 watts
Electricity Needed for 7500
750
135
hrs. of light (kWh)
Cost of Electricity (per kWh)
$1.00
$ 1.00
Total Cost of Electricity
$750.00
$135.00
Grand Total
$815.00
$160.00
Remarks:
o Grand Total = Total Cost of Bulbs + Total Cost of Electricity
o Estimated cost of an incandescent light bulb is $6.50 and that of a fluorescent
light bulb is $25.00.
Discussion
3. Deciding which bulb to buy and why
In your group, use all this information to decide which bulb is a better buy. Use
your calculations to explain your decision. What additional information would your
group like to have before making a final decision about which bulb to buy? Discuss
which bulb your group thinks most people buy when they go into a store. Why? If
your group were a manufacturer of compact fluorescent bulbs, what would you do
to get people to buy your bulbs? Think about, discuss and come to agreement on
the information your group will add to the class discussion.
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Unit 8 – Energy Use At Home
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