“Which light is right?”
Greater Essex County
District School Board
fluorescent
or
incandescent
light
?
grade 8
science
ecoschoolsproject
“Which light is right?”
1
Grade 8 Science
“Which light is right?”
Kit
Requirements
(per group)
“Which light is right?”
z
Two light bulbs (one 100 watt incandescent and
one 23 watt fluorescent)
z
One 11” by 17” blank white paper
z
One gooseneck lamp
z
One lab thermometer
z
One meter stick or ruler
z
One stopwatch or clock
2
Grade 8 Science
“Which light is right?”
Overall Expectations
8s64
Describe ways in which different sources of visible light and the properties
of light, both natural and artificial, are used by humans for different
purposes.
8s67
Describe how incandescent, fluorescent and phosphorescent sources
produce light.
Specific Expectations
8s76
Plan investigations for some of these answers and solutions, identifying
variables that need to be held constant to ensure a fair test and
identifying criteria for assessing solutions.
8s77
Use appropriate vocabulary, including correct science and technology
terminology, to communicate ideas, procedures and results (e.g., use
terms such as incidence, reflection, refraction, wavelengths and frequency
when describing the properties of light).
8s78
Compile qualitative and quantitative data gathered through investigation
in order to record and present results, using diagrams, flow charts,
frequency tables, graphs, and stem-and-leaf plots by hand or with a
computer (e.g. use light sensors to identify and record different light
intensities and present the findings in a chart).
8s79
Communicate the procedures and results of investigations for specific
purposes and to specific audiences, using media works, written notes
and descriptions, charts, graphs, drawings, and oral presentations (e.g.,
prepare a brochure informing the public of the risks of a specific type of
electromagnetic radiation).
8s85
Evaluate the effectiveness of energy transfer systems (e.g., compare the
amount of heat given off by fluorescent and incandescent bulbs).
8s86
Recognize that energy can be a significant cost in the manufacture and
use of products or systems and explain how that determines its production
(e.g., analyse the costs and benefits of producing and using solar panels).
“Which light is right?”
3
Grade 8 Science
“Which light is right?”
FACT SHEET:
Incandescent vs.
Compact Fluorescent
Imagine you home or office without light. Light allows us to see, create a comfortable environment, and be safe and secure. The lighting techniques (the ways you arrange lights, the
lamps, and the light bulbs you choose for the rooms in your home or office will make a difference in your comfort level and energy use.
Everyone knows that appliances, like your refrigerator and dishwasher, use electricity.
However, you may not realize lamps or bulbs and the fixtures in which they operate (called
luminaries) are also appliances. If we consider lighting as a single appliance, it can be as
much as 25 percent of your home’s electricity consumption.
When choosing many appliances, consumers can compare Energy Guide labels, telling
them how much it will cost each year to operate the appliance. This information allows
people to choose an appliance at a higher initial cost if they know it is more efficient and will
save them money in the long run. Not so with lamps. It is more difficult to calculate efficiency and savings because of the different lighting technologies.
It is important to understand energy use in lamps when you choose from today’s full array
of lighting technologies. The amount of light given off is measured in lumens. One lumen is
the equivalent of the light given off by one candle. A watt, on the other hand, is the amount
of electricity a light bulb uses to produce light. It is not an indication of brightness.
The distinction is important because a new 13 watt compact fluorescent light bulb produces
as much light (as many lumens) as a traditional 60 watt incandescent bulb. As much light
and only using one-quarter of the electrical energy!
That is why one of the easiest and fastest ways to cut your home or office energy bill is to
improve its lighting efficiency. If you replace 25 percent of the lights in high use areas with
fluorescents, you can save about 50 percent of your lighting energy bill.
“Which light is right?”
4
Fluorescent
Lights
Unfortunately, fluorescent lighting carries the old negative
stigma of providing flickering, sickly, green tinted, institutional,
headache causing, noisy light. If you think these lights are good
only for the garage, think again.
Times have changed. Fluorescents are not only one of the most
efficient options around, offering the longest life bulb, they come
in a variety of colours, types and sizes. Best of all, with the new
electronic ballasts, they are quiet.
Fluorescent lights are phosphor-coated glass tubes filled with an
inert gas and a small amount of mercury. Because different
brands can have different mixes of gases inside, fluorescents
produce a wide assortment of colour light that match the warm
glow of incandescents.
All fluorescent lights need a controlling ballast to operate. The
ballast alters the electric current flowing through the fluorescent
tube, activating the gas inside and causing it to glow. Newly
developed electronic ballasts eliminate that annoying flicker and
buzz that used to occur with old magnetic ballasts, which were
also heavier and less efficient. But there are now even more
impressive improvements to the design of fluorescent lights.
To create the same amount of light as an incandescent bulb, a
fluorescent tube uses only one-quarter to one-third of the energy.
Plus, fluorescents last ten to 15 times longer (10,000 hours or
more).
Compact
Fluorescent
Lights
“Which light is right?”
When these new designs were introduced in the early 1980’s, they
revolutionized lighting. A variation on the fluorescent tube,
compact fluorescents work the same way, only the tube has been
made smaller and folded over in a way to make them fit into
spaces designed for incandescent bulbs. With a screw base that
fits a normal light bulb socket, they operate on a quarter of the
energy used by incandescents, and last ten times longer.
5
Incandescents
(The Usual
Light Bulbs)
Thomas Edison invented the incandescent light bulb nearly 120
years ago, and it still works pretty much as it did then. Inside a
glass bulb, electricity heats up a wire filament, causing it to glow
and give off light. Of course, electrical heaters work in much the
same way, and that’s why more than 90 percent of the energy
produced by incandescent lights is heat, not light. As a result,
incandescents are inefficient light sources. The heat they produce
can drive up your electricity bill in hot weather if your home or
office is air-conditioned.
While regular incandescent bulbs last usually between 750 to
1,000 hours before burning out, some long-life bulbs last up to
2,500 hours. The trade off is that long-life bulbs are less energy
efficient and produce less light per watt.
Materials
Required
(per group)
z
z
z
z
z
z
Suggested
Approach
Incandescent
versus Compact
Fluorescent Bulbs
“Which light is right?”
Two light bulbs (one 100 watt incandescent and one
23 watt fluorescent)
One 11” by 17” blank white paper
One gooseneck lamp
One lab thermometer
One meter stick or centimetre ruler
One stopwatch or clock (if necessary)
Before beginning the experiment, read the following information
with the students.
Bulb type
100W incandescent 23W compact fluorescent
Purchase price
$0.75
$11.00
Life of the bulb
750 hours
10,000
Number of hours burned per day
4 hours
4 hours
Number of bulbs needed
about 6 over 3 years 1 over 6.8 years
Total cost of bulbs
$4.50
$11.00
Lumens produced
1,690
1,500
Total cost of electricity
$35.04
$8.06
(8 cents / kilowatt-hour)
Your total cost over 3 years
$39.54
$19.06
Total savings over 3 years with the compact fluorescent $20.50
Source: US Department of Energy, Energy Information Administration
6
Procedure
1. On a flat surface, lay the 11” by 17” paper down and put the
gooseneck lamp at the edge of it.
2. Put the thermometer 30 cm from the lamp and lay it down on
the paper.
3. Make sure the lamp is unplugged and screw in the 23 watt
fluorescent bulb.
4. Measure the temperature and record it in Table 1 before
turning the light on. Predict what the temperature will be
after leaving the light on for five minutes. Record this in
Table 1.
5. Turn on the light and leave it shining on the paper for exactly
five minutes.
6. After five minutes have elapsed, take the temperature again
and record it in Table 1.
7. Shut off the light after taking the reading and let it cool down
for a few minutes (five to ten minutes).
8. Calculate the range of the temperatures and record it in Table
1.
9. Repeat steps 1. to 8. for the 100 watt incandescent bulb.
Note: As the students wait for the bulb to cool down, have them
reread the Fact Sheet: Incandescent versus Compact
Fluorescent Lights in their groups and answer the attached
worksheet.
Caution: HOT!
“Which light is right?”
7
Table #1
“Which light is right?”
Type of
light bulb
Initial
temperature
(Celcius)
Temperature after
5 minutes
Predicted
Actual
Range
fluorescent
incandescent
Observations
“Which light is right?”
8
Worksheet #1
Incandescent versus Fluorescent Light Bulbs
Name: _____________________________________________ Date: _______________________
1.
The amount of light given off is measured in
2.
One lumen is the amount of light given off by
3.
The amount of electricity that is used to create light
is measured in
4.
If one out of four incandescent lights is replaced with
a fluorescent, the energy used would be cut by
5.
In an incandescent light bulb ________ of energy is
wasted to create heat - not light.
6.
Fluorescent lights are basically glass tubes filled with
inert
7.
Electricity flows through the gas, causing it to
8.
New compact fluorescent light bulbs use about _______
of the energy used by a regular incandescent light.
9.
Fluorescent light bulbs last about ________ times
longer than incandescent bulbs.
%
10. An incandescent bulb will last about
hours
11. A compact fluorescent bulb will last about
hours
12. A incandescent bulb will last about
year
years
A fluorescent bulb will last about
13. In four years, the cost of electricity to use an
incandescent bulb is
The cost to use a fluorescent bulb in the same amount
of time is
14. Based on a cost of 8 cents per kwh, a person would
save ________ over three years for each fluorescent
bulb used.
“Which light is right?”
$
$
$
9
Worksheet #1 - ANSWERS
Incandescent versus Fluorescent Light Bulbs
Name: _____________________________________________ Date: _______________________
1.
The amount of light given off is measured in
lumens
2.
One lumen is the amount of light given off by
one candle
3.
The amount of electricity that is used to create light
is measured in
4.
If one out of four incandescent lights is replaced with
a fluorescent, the energy used would be cut by
half
5.
In an incandescent light bulb ________ of energy is
wasted to create heat - not light.
90 %
6.
Fluorescent lights are basically glass tubes filled with
inert
gas
7.
Electricity flows through the gas, causing it to
8.
New compact fluorescent light bulbs use about _______
of the energy used by a regular incandescent light.
9.
Fluorescent light bulbs last about ________ times
longer than incandescent bulbs.
10. An incandescent bulb will last about
11. A compact fluorescent bulb will last about
12. A incandescent bulb will last about
A fluorescent bulb will last about
13. In four years, the cost of electricity to use an
incandescent bulb is
The cost to use a fluorescent bulb in the same amount
of time is
14. Based on a cost of 8 cents per kwh, a person would
save ________ over three years for each fluorescent
bulb used.
“Which light is right?”
watts
glow
one-quarter
10
750 hours
10,000 hours
half a year
7 years
$ 35.04
$ 8.06
$ 20.50
10