ecoschoolsproject Which light is right? fluorescent or incandescent light? grade 8 science Greater Essex County District School Board

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1 Which light is right? Greater Essex County District School Board fluorescent or incandescent grade 8 science light? ecoschoolsproject Which light is right? 1

2 Grade 8 Science Which light is right? Kit Two light bulbs (one 100 watt incandescent and Requirements one 23 watt fluorescent) (per group) One 11 by 17 blank white paper One gooseneck lamp One lab thermometer One meter stick or ruler One stopwatch or clock Which light is right? 2

3 Grade 8 Science Which light is right? Overall Expectations 8s64 8s67 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. Describe how incandescent, fluorescent and phosphorescent sources produce light. Specific Expectations 8s76 8s77 8s78 8s79 8s85 8s86 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. 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). 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). 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). Evaluate the effectiveness of energy transfer systems (e.g., compare the amount of heat given off by fluorescent and incandescent bulbs). 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

4 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

5 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 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. Which light is right? 5

6 Incandescents Thomas Edison invented the incandescent light bulb nearly 120 (The Usual Light Bulbs) 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 Two light bulbs (one 100 watt incandescent and one Required 23 watt fluorescent) (per group) 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) Suggested Approach Incandescent versus Compact Fluorescent Bulbs 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 Which light is right? 6

7 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 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 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 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

8 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

9 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 11. A compact fluorescent bulb will last about 12. A incandescent bulb will last about A fluorescent bulb will last about hours hours year years 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

10 Worksheet #1 - ANSWERS 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 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. lumens one candle watts half 90 % gas glow one-quarter hours 10,000 hours half a year 7 years $ $ 8.06 $ Which light is right? 10