Cost of electricity varies but typical values are around exist0.15/kWh. Using th
ID: 2077990 • Letter: C
Question
Cost of electricity varies but typical values are around exist0.15/kWh. Using this price, calculate the cost of (a) running a load of laundry through a dryer that takes 42.0 min and draws 5, 300-W, (b) making a piece of toast in 3.00 min with a 980-W toaster, and (c) leaving a 50.0-W light on for two weeks. (d) For each of the previous cases, calculate how high you could lift your textbook if the process to convert the energy was 40% efficient. (e) For each of the cases in parts (a) through (c), how much 100 degree C water could you vaporize?Explanation / Answer
a) 5.3 * 42/60 * 0.15 = $0.5565
b) 0.98 * 0.15 * 3 / 60 = $0.00735
c) 2 * 24 * 7 * 0.05 * 0.15 = $2.52
d) Lets assume text book weigh as 3.5 lbs
energy consumed in first case is 5300 * 42 * 60 joules = 13356000 joules
you can lift 3.5 / 2.2 * 9.8 * h = 13356000 * 0.4
h = 342,661.22 mtrs
energy in second case is 3 * 60 * 980
Hence h = 3 * 60 * 980 * 0.4 * 2.2 / 9.8 / 3.5
= 4525.71 m
in third case
h = 2 * 7 * 24 * 3600 * 50 * 0.4 * 2.2 / 9.8 / 3.5
= 1551673.47 m
e)
water vapourization = 2260 J /gm
= 2260000 J / kg
13356000 = 2260000 * x
x = 5.91kg water
second case
3 * 60 * 980 / 2260000 = 0.078 kg
third case
2 * 7 * 24 * 3600 * 50 / 2260000
= 26.76kg