EGEE 102 Lesson 6
Approximately what percentage of electricity does an incandescent light bulb convert into visible light?
A ) 0.05 Incandescent light bulb has an efficiency of 5%
A 75-watt light bulb produces 5 watts of radiant energy and 70 watts of heat energy. What is its efficiency?
A ) 0.0667 Efficiency = 5/75 = 0.0667
A 120-watt light bulb is left on for 24 hours. How much did it cost to operate the light bulb if electricity costs 6 cents per kWh?
A ) 0.17 Energy consumed = 120 / 1000 x 24 = 2.88 kWh Energy cost = 2.88 x 6 / 100 = $0.1728
The kitchen in your house measures 9 ft by 14 ft. You need to have 50 footcandles of illumination in the room. How many 40 watt bulbs will be required if one bulb emits 485 lumens. (1 footcandle = 1 lumen/sq.ft)
A ) 13 bulbs Area of the room = 9 x 14 = 126 sq.ft Lumens required = 50 x 126 = 6300 lumens # of bulbs required = 6300/485 = 12.9 bulbs
The kitchen in your house measures 5 ft by 11 ft. You need to have 50 footcandles of illumination in the room. How many 75 watt bulbs will be required if one bulb emits 1375 lumens. (1 footcandle = 1 lumen/sq.ft)
A ) 2 bulbs Area of the room = 5 x 11 = 55 sq.ft Lumens required = 50 x 55 = 2750 lumens # of bulbs required = 2750/1375 = 2 bulbs
In a typical residential or commercial lighting installation, what percentage of the energy is wasted by obsolete equipment, inadequate maintenance, or inefficient use?
A ) 50 % or more In a typical residential or commercial lighting installation, 50% or more energy is wasted by obsolete equipment, inadequate maintenance, or inefficient use
Heather is a smart person who wants to save energy and money. So, she has replaced the 120 Watt incandescent light bulb in her house with a 28 Watt CFL bulb. The expected life of incandescent and CFL bulbs is 800 h and 8000 hours respectively. The purchase price of an incandescent bulb is $0.67 and for the CFL it is $5.71. The cost of electricity is 7 cents per kWh. What is her total savings over the life of the CFL bulb?
A ) 52.51 CFL energy cost for 8000 hrs = 28 / 1000 x 8000 x 7/100 = $15.68 Total cost for CFL = 5.71 + 15.68 = $21.39 Incandescent light energy cost for 8000 hrs = 120/ 1000 x 8000 x 7/100 = $67.2 # of Incandescent bulbs required = 8000/800 = 10 bulbs Total cost for Incandescent light = (0.67 x 10) + 67.2 = $73.9 Total Savings = 73.9-21.39 = $52.51
A 27 watt compact fluorescent lamp (CFL) produces 1531 lumens of light. What is the efficacy of the CFL (in lumens/watt)?
A ) 56.7 lumens/watt Efficacy = 1531/27 = 56.703 lumens/watt
Which of the following statements is true?
A ) Compact fluorescent light (CFL) bulbs are expensive initially but save money over their life time Compact fluorescent light (CFL) bulbs are expensive initially but save money over their life time
Which of the following statements is true? A ) Compact fluorescent light (CFL) bulbs are expensive initially but save money over their life time B ) Incandescent light bulb are inexpensive so they save money over their life time C ) Halogen bulbs provide bright light so they save money over their lifetime
A ) Compact fluorescent light (CFL) bulbs are expensive initially but save money over their life time Compact fluorescent light (CFL) bulbs are expensive initially but save money over their life time
What type of light does not require a ballast?
A ) Incandescent Incandescent light does not require a ballast
Compared to ordinary incandescent bulbs, tungsten halogen bulbs consume _____ power to produce same amount of light.
A ) Lesser Compared to ordinary incandescent bulbs, tungsten halogen bulbs consume lesser power to produce same amount of light.
CFL bulbs operate at _____ temperatures compared to halogen bulb.
A ) Much lower CFL bulbs operate at much lower temperatures compared to halogen bulb.
The high-pressure sodium (HPS) lamp is widely used for what purpose?
A ) Outdoor and industrial applications HPS lamp is widely used for outdoor and industrial applications
CFL lights operate at the same voltage as standard incandescent lights.
A ) TRUE CFLs can replace incandescent bulbs that are roughly 3 to 4 times their wattage but can cost up to 10 times more than comparable incandescent bulbs. But voltage rating is the same
Compact fluorescent light operated at cold temperatures (under around 50-60 degrees F) may result in reduced light output.
A ) TRUE Compact fluorescent light operated at cold temperatures (under around 50-60 degrees F) may result in reduced light output
Tungsten-halogen lamps operate at very high temperatures (high enough to literally fry eggs) and should not be used in fixtures that have paper- or cellulose-lined sockets.
A ) TRUE Tungsten-halogen lamps operate at very high temperatures (high enough to literally fry eggs) and should not be used in fixtures that have paper- or cellulose-lined sockets
What kind of information does a life-cycle cost (LCC) analysis provide?
A ) Total cost of a lighting system-including all expenses incurred over the life of the system Lifecycle cost analysis provides total cost of a lighting system-including all expenses incurred over the life of the system
A foot-candle (fc) is defined as _____.
A ) a lumen of light distributed over 1 square foot area A foot-candle (fc) is defined as a lumen of light distributed over 1 square foot area
General purpose lighting in hallways is also called _____ lighting.
A ) ambient General purpose lighting in hallways is also called ambient lighting
A higher CRI means _____.
A ) better color rendering A higher CRI means better color rendering
Use of which one of these devices for lighting leads to reduction in electricity consumption?
A ) dimmers Dimmers for lighting can reduce electricity consumption
A footcandle (fc) is the standard unit of measure for illumination on a surface. It is calculated as _____.
A ) fc = Lumens of Light / Area in sq. ft fc = Lumens of Light / Area in sq. ft
Which one of the following methods of lighting is least efficient?
A ) incandescent Incandescent light bulbs are the least efficient
A 100 watt incandescent light bulb is operated for 11 hours, and a 32 watt fluorescent light bulb is operated for the same period of time. At 8 cents per kWh, what is the cost savings in using the fluorescent bulb?
B ) 0.06 Incandescent light bulb Energy consumed = 100/1000 x 11 = 1.1 kWh Energy Cost = 1.1 x 8/100 = $0.088 Fluorescent light bulb Energy consumed = 32/1000 x 11 = 0.352 kWh Energy Cost = 0.352 x 8/100 = $0.02816 Savings in Energy Cost = 0.088-0.02816 = $0.05984
A 100 watt incandescent light bulb is operated for 12 hours, and a 15 watt fluorescent light bulb is operated for the same period of time. At 10 cents per kWh, what is the cost savings is using the fluorescent bulb?
B ) 0.1 Incandescent light bulb Energy consumed = 100/1000 x 12 = 1.2 kWh Energy Cost = 1.2 x 10/100 = $0.12 Fluorescent light bulb Energy consumed = 15/1000 x 12 = 0.18 kWh Energy Cost = 0.18 x 10/100 = $0.018 Savings in Energy Cost = 0.12-0.018 = $0.102
The luminous efficacy of a tungsten lamp is about 12 lumens/watt. What is the efficacy of a fluorescent tube (in lumens/watt)?
B ) 50 luminous efficacy of fluorescent tube is typically 3-4 times more than tungsten lamp
By approximately what percentage can lighting energy costs be reduced with the use of modern technology?
B ) 50 percent Use of modern technology can reduce lighting energy cost to half
For an Incandescent bulb, initial cost may be high but the energy costs will be low over its life time.
B ) FALSE For a CFL, initial cost may be high but the energy costs will be low over its life time.
Higher Wattage bulbs are less efficient than lower Wattage bulbs.
B ) FALSE Higher wattage bulbs have higher efficiency compared to lower wattage bulbs
Higher Wattage incandescent bulbs are less efficient than lower Wattage incandescent bulbs.
B ) FALSE Higher wattage incandescent bulbs are more efficient than lower wattage incandescent bulbs
Incandescent lights operate at the same wattage as fluorescent lights to give out the same amount of light.
B ) FALSE Incandescent lights operate at a much higher wattage than fluorescent lights to give the same amount of light output
Filaments in fluorescent bulbs are made of tungsten.
B ) FALSE There is no filament in Fluorescent bulb
Which one of the following light bulb produces lowest lumens per watt?
B ) Incandescent Incandescent light bulb has the lowest lumens per watt
Which one of the following light bulb produces lowest lumens per watt?`
B ) Incandescent Incandescent light bulb has the lowest lumens per watt
The most common measure of light output (or luminous flux) is the _____.
B ) Lumen The most common measure of light output (or luminous flux) is the lumen
Which of the following kind of bulb requires a ballast?
B ) fluorescent Fluorescent bulb requires a ballast
What type of bulb is usually filled with a mixture of inert gases and mercury?
B ) fluorescent Fluorescent bulbs are filled with a mixture of inert gases and mercury
Vapors of which element are used to fill energy efficient bulbs?" A ) potassium B ) mercury C ) hydrogen D ) halogen
B ) mercury Mercury vapor is used to fill energy efficient bulbs
A 80 watt incandescent light bulb is operated for 15 hours, and a 15 watt fluorescent light bulb is operated for the same period of time. At 10 cents per kWh, what is the cost savings in using the fluorescent bulb?
C ) 0.1 Incandescent light bulb Energy consumed = 80/1000 x 15 = 1.2 kWh Energy Cost = 1.2 x 10/100 = $0.12 Fluorescent light bulb Energy consumed = 15/1000 x 15 = 0.225 kWh Energy Cost = 0.225 x 10/100 = $0.0225 Savings in Energy Cost = 0.12-0.0225 = $0.0975
Compact fluorescent lamps are how many times more efficient than incandescent lamps producing an equivalent light output?
C ) 2-4 times more efficient
Typically, compact fluorescent lamps are how many times more efficient than incandescent lamps?
C ) 3-4 times more efficient
The kitchen in your house measures 5 ft by 10 ft. You need to have 50 footcandles of illumination in the room. How many 40 watt bulbs will be required if one bulb emits 500 lumens. (1 footcandle = 1 lumen/sq.ft)
C ) 5 bulbs Area of the room = 5 x 10 = 50 sq.ft Lumens required = 50 x 50 = 2500 lumens # of bulbs required = 2500/500 = 5 bulbs
Efficacy of lighting is measured by _____.
C ) Lumens per Watt Efficacy of lighting is measured by lumens per watt
Efficacy of lighting is measured in _____.
C ) Lumens per Watt Efficacy of lighting is measured in lumens per watt
CFL operate at _____________ temperatures when compared to a halogen bulb.
C ) Much lower CFL operate at much lower temperatures when compared to a halogen bulb
Fluorescent light is produced by _____.
C ) converting UV to visible light Fluorescent light is produced by converting UV to visible light
Which of the following lighting methods is the most energy efficient?
C ) high intensity discharge HID lamps are the most energy efficienct
A 100 watt incandescent light bulb is operated for 7 hours, and a 32 watt fluorescent light bulb is operated for the same period of time. At 8 cents per kWh, what is the cost savings in using the fluorescent bulb?
D ) 0.04 Incandescent light bulb Energy consumed = 100/1000 x 7 = 0.7 kWh Energy Cost = 0.7 x 8/100 = $0.056 Fluorescent light bulb Energy consumed = 32/1000 x 7 = 0.224 kWh Energy Cost = 0.224 x 8/100 = $0.01792 Savings in Energy Cost = 0.056-0.01792 = $0.03808
What is the minimum amount of illumination that is required for reading?
D ) 50 fc A minimum of 50 fc of illumination is required for reading
Heather is a smart person who wants to save energy and money. So, she has replaced the 120 Watt incandescent light bulb in her house with a 28 Watt CFL bulb. The expected life of incandescent and CFL bulbs is 800 h and 8000 hours respectively. The purchase price of an incandescent bulb is $0.75 and for the CFL it is $4.14. The cost of electricity is 7 cents per kWh. What is her total savings over the life of the CFL bulb?
D ) 54.88 CFL energy cost for 8000 hrs = 28 / 1000 x 8000 x 7/100 = $15.68 Total cost for CFL = 4.14 + 15.68 = $19.82 Incandescent light energy cost for 8000 hrs = 120/ 1000 x 8000 x 7/100 = $67.2 # of Incandescent bulbs required = 8000/800 = 10 bulbs Total cost for Incandescent light = (0.75 x 10) + 67.2 = $74.7 Total Savings = 74.7-19.82 = $54.88
A 23 watt compact fluorescent lamp (CFL) produces 1335 lumens of light. What is the efficacy of the CFL (in lumens/watt)?
D ) 58.04 lumens/watt Efficacy = 1335/23 = 58.043 lumens/watt
Heather is a smart person who wants to save energy and money. So, she has replaced the 100 Watt incandescent light bulb in her house with a 23 Watt CFL bulb. The expected life of incandescent and CFL bulbs is 800 h and 8000 hours respectively. The purchase price of an incandescent bulb is $0.52 and for the CFL it is $6.73. The cost of electricity is 10 cents per kWh. What is her total savings over the life of the CFL bulb?
D ) 60.07 CFL energy cost for 8000 hrs = 23 / 1000 x 8000 x 10/100 = $18.4 Total cost for CFL = 6.73 + 18.4 = $25.13 Incandescent light energy cost for 8000 hrs = 100/ 1000 x 8000 x 10/100 = $80 # of Incandescent bulbs required = 8000/800 = 10 bulbs Total cost for Incandescent light = (0.52 x 10) + 80 = $85.2 Total Savings = 85.2-25.13 = $60.07
Compact fluorescent light usually has a _____ compared to an incandescent bulb producing the same number of lumens.
D ) Longer life Compact fluorescent light usually has a longer life compared to an incandescent bulb producing the same number of lumens
Which one of the following light bulbs produces highest lumens per watt?
D ) Low pressure sodium Low pressure sodium light bulbs produce highest lumens per watt
Which one of the following light bulbs produces highest lumens per watt? A ) Incandescent B ) Fluorescent C ) Compact fluorescent light D ) Low pressure sodium
D ) Low pressure sodium Low pressure sodium light bulbs produce highest lumens per watt
What are the units of measuring light?
D ) Lumens Light is measured in lumens
Fluorescent bulbs are filled with _____.
D ) a mixture of argon-krypton gas and a small amount of mercury Fluorescent bulbs are filled with a mixture of argon-krypton gas and a small amount of mercury
Light bulb labels should contain what kind of information?
D ) all of the above Light bulb labels should contain light output, energy used and life of the bulb
Which of the following is not a factor affecting the number of lamps required? A ) Fixture efficiency B ) Lamp lumen output C ) Room size and shape D ) Availability of natural light E ) # of people in the room
E ) # of people in the room Fixture efficiency, lamp lumen output, room size and shape, availability of natural light are factors affecting the number of lamps required
Fluorescent bulbs ultimately give out UV light.
FALSE Fluorescent bulbs convert UV to visible light
Daylighting typically has a CRI value of 100.
TRUE Daylighting typically has a CRI value of 100
A spotlight is typically of what type?
Type-R Typically, Type-R lamps are used for spotlight
Efficacy of lighting is measured in _____.
lumens per watt
