An energy-efficient bulb claims to have the brightness of a 75 W bulb but only uses 15 W of electrical power.?
An energy-efficient bulb claims to have the brightness of a 75 W bulb but only uses 15 W of electrical power.
(a) If you have this light bulb on for 8 hours a day, for 360 days during a year, how many hours is it on?
_____hours
(b) A kilowatt is 1000 watts. The kilowatt-hour is a common unit for energy, obtained by multiplying the power in kilowatts by the time used in hours. How many kilowatt-hours (kWh) will you use when burning the 75 W bulb for the year?
____kWh
(c) How many kilowatt-hours (kWh) will you use when burning the 15 W bulb for the year?
_______kWh
(d) Assuming that the cost of electricity is 12¢ per kWh, what is the cost of using the 75 W bulb for the year?
$______
(e) Assuming this same cost, what is the cost of using the 15 W bulb for the year?
$_____
(f) How much do you save by using the 15 W bulb?
$______
(g) How much would you save if you replaced 20 of the 75 W bulbs with the 15 W bulbs?
$_______
One Response
pinoypangit
15 Jun 2010
a) 300 * 8 = 2880hours
b)(1kw/1000w)*(75w)(2880 hrs) = 216 kw
c))(1kw/1000w)*(15w)(2880 hrs) = 43.2kw
d)(216kw)*($0.12) = $25.92
e)(43.2kw)*($0.12) = $5.18
f) 25.92-5.18 = $20.74
g)($20.74)*(20bulbs) = $414.72..Now this is the savings in 20 bulbs. The answers above (a-f) are for ONE bulb.
Sige…..