quiz lesson 6

# Incandescent lights a

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: rescent lamp (CFL) produces 1839 lumens of light. What is the efficacy of the CFL (in lumens/watt)? Correct C ) 61.3 lumens/watt Efficacy = 1839/30 = 61.3 lumens/watt 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? Correct 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 75- watt light bulb produces 5 watts of radiant energy and 70 watts of heat energy. What is its efficiency? Correct A ) 0.0667 Efficiency = 5/75 = 0.0667 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? Correct 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 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) Correct 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 For an Incandescent bulb, initial cost may be high but the energy costs will be low over its life time. C...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online