quiz lesson 6

# A tungsten lamp is about 12 lumenswatt

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Unformatted text preview: 1. The cost of electricity is 7 cents per kWh. What is her total savings over the life of the CFL bulb? Correct D ) 35.31 CFL energy cost for 8000 hrs = 13 / 1000 x 8000 x 7/100 = \$7.28 Total cost for CFL = 5.31 + 7.28 = \$12.59 Incandescent light energy cost for 8000 hrs = 75/ 1000 x 8000 x 7/100 = \$42 # of Incandescent bulbs required = 8000/800 = 10 bulbs Total cost for Incandescent light = (0.59 x 10) + 42 = \$47.9 Total Savings = 47.9- 12.59 = \$35.31 Approximately what percentage of electricity does an incandescent light bulb convert into visible light? Correct A ) 0.05 Incandescent light bulb has an efficiency of 5% Compared to ordinary incandescent bulbs, tungsten halogen bulbs consume _____ power to produce same amount of light. Correct A ) Lesser Compared to ordinary incandescent bulbs, tungsten halogen bulbs consume lesser power to produce same amount of light. The kitchen in your house measures 6 ft by 12 ft. You need to have 50 footcandles of illumination in the room. How many 40 watt bulbs will be required if one bulb emits 515 lumens. (1 footcandle = 1 lumen/sq.ft) Correct D ) 7 bulbs Area of the room = 6 x 12 = 72 sq.ft Lumens required = 50 x 72 = 3600 lumens # of bulbs required = 3600/515 = 6.9 bulbs 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? Correct A ) 0.17 Energy consumed = 120 / 1000 x 24 = 2.88 kWh Energy cost = 2.88 x 6 / 100 = \$0.1728 Compact fluorescent light operated at cold temperatures (under around 50- 60 degrees F) may result in reduced light output. Correct A ) TRUE Compact fluorescent light operated at cold temperatures (under around 50- 60 degrees F) may result in reduced light output A 19 watt compact fluorescent lamp (CFL) produces 1869 lumens of light. What is the efficacy of the CFL (in lumens/watt)? Correct A ) 98.37 lumens/watt Efficacy = 1869/19 = 98.368 lumens/watt Fluorescent bulbs are filled with _____. Correct D ) a mixture of argon- krypton gas and a small amount of mercury...
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