Get the information you need with the help of IDNLearn.com's expert community. Our platform offers comprehensive and accurate responses to help you make informed decisions on any topic.

Here is the formatted question with superscript and subscript without using LaTeX:

(a) Starting from the Principle of Energy Conservation, explain the reasoning that gives us the expression for thermodynamic efficiency, η, in terms of the temperatures TC and TH. You may assume the Carnot relation, QC / QH = TC / TH, for an ideal heat engine.
(b) What is a heat engine?