In a certain city, electricity costs $0.15 per kW·h. What is the annual cost for
ID: 574363 • Letter: I
Question
In a certain city, electricity costs $0.15 per kW·h. What is the annual cost for electricity to power a lamp-post for 5.50 hours per day with (a) a 100.-watt incandescent light bulb (b) an energy efficient 25-watt fluorescent bulb that produces the same amount of light? Assume 1 year = 365 days.
a).100 watt bulb. b). 25 watt bulb
(c) A typical incandescent bulb costs $0.89 and lasts for about a year; a typical energy efficient fluorescent bulb costs about $3.49 and lasts for about 3 years. Is the additional cost of the fluorescent bulb justified?
yes or no
please show works and explanation
Explanation / Answer
1kW.h = 1kilo watt of Electrical energy consumption per hour
1Watt = 1Jule per scond
1kilo watt= 1000Jule per second
1kilo watt hour = 3600000Jules
a)
Answer
$29.7
Explanation
100watt used for 1hour = 100watt - hour =0.1kW.h
duration of lamp per day = 5.50hours
Total duration per annum = 365 × 5.50hours = 1980hours
total power consumption per annum = 1980 × 0.1kW.h = 198 kW.h
cost per annum = 198kW.h × $0.15 = $29.7
b)
Answer
$7.425
Explanation
25 watt used for 1hour = 25 watt- hour = 0.025kW.h
Total duration of bulb = 1980
Total power consumption per annum = 1980×0.025kW.h = 49.5kW.h
Cost per annum = $0.15 × 49.5 = $7.425
c)
Answer
yes
Explanation
power consumption of incandescent lamp per annum = 198kW.h
cost of power =$ 29.7
Cost of lamp = $0.89
Total cost = $30.59
Cost per year = $30.59
power consumbtion of flourescent lamp per annum = 49.5kW.h
for 3 years = $148.5
cost of power = $7.425 × 3 = $22.275
cost of lamp = $3.49
total cost = $25.765
cost per year = $8.588
For flourescent lamp usage cost per year is much less comparing to incandescent lamp
Therefore,
Additional cost of flourescent bulb is justified
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