In a certain city, electricity costs $0.17 per kW·h. What is the annual cost for
ID: 1024406 • Letter: I
Question
In a certain city, electricity costs $0.17 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.(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?
Explanation / Answer
electricity costs = $0.17 per kWh
(a) step-1:100.-watt incandescent light bulb for 5.50 hours per day, caluculation as follows
--> 100watts x 5.5 hours = 550 watts- hours per day
step-2 : but electricty measure in kilowatt hours on electricity bill, hence how many kWh a 100-watt incadesent bulb uses is diveded by 1,000
--> 550 watts-hours per day /1000 = 0.550 kWh per day
step-3 : 100-watt incandescent bulb useage over a year
-->0.550kWh per day x 365 days ( 1 year ) = 200.75 kWh per year
step-4: figuring out the cost, according given data electricity cost $0.17 kWh
hence , 200.75 kWh per year x $0.17 kWh = $34.13 per year
so, Annual cost for electricity to power lamp -post for 5.50hours per day with a 100 watt incandescent light bulb is $34.13
(b)
step-1:25.-watt flouorescent light bulb for 5.50 hours per day, caluculation as follows
--> 25watts x 5.5 hours = 137.5 watts- hours per day
step-2 : but electricty measure in kilowatt hours on electricity bill, hence how many kWh a 100-watt flouorescent bulb uses is diveded by 1,000
--> 137.5 watts-hours per day /1000 = 0.1375 kWh per day
step-3 : 25-watt fluorescent bulb useage over a year
-->0.1375 kWh per day x 365 days ( 1 year ) = 50.1875 kWh per year
step-4: figuring out the cost, according given data electricity cost $0.17 kWh
hence , 50.1875 kWh per year x $0.17 kWh = $8.54 per year
so, Annual cost for electricity to power lamp -post for 5.50 hours per day with a 25-watt fluorescent bulb is $8.54
(c)
incadescent light bulb produce electric light with a thin filmant made with tungsten meatal and fluorescent bulb produces light by a physical thermo ionic process of mercury lamp
from the above table , fluorescent bulb is more expensive than incandescent light bulb.
but, fluorescent bulb have longer life than incandescent light bulb,
hence according to the given data, "the additional cost of the fluorescent bulb is justifiesd"
incandesent light bulb fluorescent bulb luminous efficiency is low luminous efficiency is high have a shorter life have a longer life cheap more expensive