(a) In the ENGR 10 lab (E391), there are 50 long light bulbs (P = 100 W) and 30
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Question
(a) In the ENGR 10 lab (E391), there are 50 long light bulbs (P = 100 W) and 30 regular bulbs (P = 60 W). How much energy is consumed lighting the lab during the 3 hour lab period. Calculate the amount of energy saved if all bulbs are replaced by CFL (spiral) bulbs (P = 25W). Continuing from (a), calculate the amount of natural gas (ft^3) needed to provide the energy to keep the lights (long + regular) in the E391 lab on overnight for a month (10 hours per day for 30 days)? In other words, how much extra energy (in terms of cubic feet of natural gas) does SJSU have to purchase when we don't turn off the lights in a lab.Explanation / Answer
Total power of 50 long light bulbs = 50 x 100 W = 5000 W
Total power of 30 regular bulbs = 30 x 60 W = 1800 W
so total power by both type of bulbs = 6800 W
so energy dissipated during 3 hours (E1) = 6800 x 3 = 20400 Wh = 20.4 kWh
If all the bulbs are replaced by CFL so total power of CFL = 80 x 25 W = 2000 W
total enery by CFLs in 3 hours (E2) = 2000 x 3 = 6000 Wh = 6kWh
so saving in energy (E1-E2) = 20.4 kWh - 6kWh = 14.4 kWh
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