- #1
chipM
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Homework Statement
1)Wally whacko claims to have invented a heat engine that will revulutionalise the industry. It runs between a hot source at 300 C and a cold sink at 25 C . he claims that his engine is 92 % effieicnt.
What is the max efficiency of his engine ? in 2sf
(2)At a certain location the solar power per unit area reaching Earth suface is 200 w/m^2. Averaged over 24 hour day.
If the average requirement in your home is 3.8 kw and you can convert solar power to elevtric power with 10% efficiency, how large a collector area will you need to meet all your house hold energy requirement from solar energy.
(3)The soecific heat capacity of ice is about 0.5 cal/g C.
Suppose that it remains at that value all the way to absolute zero. Calculate the number of calories it would take to change a 0.90g ice cube at absolute zero ( -273 C) t 0.90 g of boiling water.
How does this number of calories compare with the number of calories required to change the same gram of 100 C boiling water to 100 C steam. ?
Homework Equations
1) t(h)-t(c)/ t(h)
i don't know number 2
3) q=mct
The Attempt at a Solution
1) 300-25 /300 = 91.667 so its 91.667% efficeint
2) idont know where to start
3) o.90 x -273 x 0.5= -122.850
are they right ? please correct me if i am wrong with proper working
thanks !