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?

Which statement best describes how the $2^{nd}$ law of thermodynamics relates to the operation of heat engines?

Which statement most accurately describes the second law of thermodynamics?

According to the second law of thermodynamics, which of the following actions will increase the maximum possible efficiency of a heat engine operating between two thermal reservoirs?

A heat engine absorbs $500J$ of heat from a high-temperature reservoir and expels $390J$ of heat to a low-temperature reservoir in each cycle. What is the approximate efficiency of the heat engine?

A Carnot refrigerator is operated between two heat reservoirs at temperatures of $320$ K and $270$ K. If in each cycle the refrigerator receives $415$ J of heat energy from the reservoir at $270$ K, how many joules of heat energy does it deliver to the reservoir at $320$ K?

An aircraft engine takes in 9 kJ of heat and expels 6.4 kJ of heat each cycle. How much mechanical work does the engine do each cycle?

A heat engine uses a tank of ice water as a cold reservoir. The engine takes in 8 kJ of heat from the hot reservoir, and the heat expelled melts 18g of ice in the tank. How much work does this engine do?

A steam turbine takes in 75g of water and boils it as heat energy to run a 40% efficient engine. How much work does this engine do per cycle?