🚀 go-pugleaf

To all,

In Hewitt's conceptual physics he asks the following question:

Which heat engine has the greater ideal efficiency; one that operates
between the temp. 600 K and 400 K, or one that operate between 500 K and
300 K?  Explain how your answer conforms to the idea that a higher
operating temp. yeilds higher efficiency.

--
I understand the first part of the question -- the first engine has an
eff. of .33 and the second .40.  But that says the cooler temp. is more
efficient, which contradicts the second answer.  In the Teachers edition
Hewitt says ---"when we say an engine is more efficient at a higher
operating temperature, we are refering to change in T -- a higher
operating temp. compared to exhaust temp."   This confuses me.  I see
that 600 - 400 = 200 and this (200) is not as close to the exhaust temp
(400) as is 500  - 300 = 200 (exhaust is 300).  But if I use an exhaust
of 0 for the second case the engine is 100% efficient.  And the delta T
is 500 -- far from the exhaust of 0 -- so it should be less efficient
accroding to Hewitt's explaination.

I don't get this stuff.  Could someone explain it to me???

Doug Benning
benning@tenet.edu