23. The Second Law of Thermodynamics

Which of the following best defines the thermal efficiency of a heat engine?

To increase the maximum efficiency of a heat engine operating between two thermal reservoirs, which of the following should be done according to the second law of thermodynamics?

Why must every heat engine have a cold reservoir?

Which of the following best completes the sentence: A heat engine is a device that uses $Q$ to produce useful work?

A heat engine absorbs $500J$ of heat from a hot reservoir and does $200J$ of work in one cycle. How much heat is exhausted to the cold reservoir?

In a modern power plant, how is heat energy typically used to generate electricity?

Why is thermal energy produced by a heat engine not generally usable to do work?