B.4 True/False Heat Engines and Carnot Cycle

A closed loop in a pressure-volume diagram represents a cyclic process.

• False

• True

• Only for isothermal processes

• Only for adiabatic processes

A heat engine does net work on the surroundings by converting thermal energy into work.

• A heat engine converts thermal energy into work.

• A heat engine only produces heat.

• A heat engine cannot convert thermal energy.

• A heat engine absorbs work from the surroundings.

A heat pump does not do work on the surroundings.

• A heat pump generates energy for the surroundings.

• A heat pump requires external work to operate.

• True

• False

The Carnot cycle consists of four processes: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression.

• The Carnot cycle consists of isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression.

• adiabatic expansion, isothermal expansion, adiabatic compression, isothermal compression

• isothermal expansion, isothermal compression, adiabatic expansion, adiabatic compression

• isothermal expansion, adiabatic compression, isothermal compression, adiabatic expansion

The Carnot cycle is considered the most efficient cycle because it operates between two temperature reservoirs without any entropy generation.

• The Carnot cycle is the least efficient cycle due to high entropy generation.

• The Carnot cycle is the most efficient cycle because it operates without any entropy generation.

• The Carnot cycle operates between three temperature reservoirs for maximum efficiency.

• The Carnot cycle generates entropy to improve its efficiency.

Entropy in a thermodynamic system always decreases over time.

• Entropy in a thermodynamic system always increases over time.

• Entropy remains constant in a thermodynamic system.

• Entropy can only decrease in isolated systems.

• False

Not all thermal energy can be converted into useful work due to the second law of thermodynamics.

• The first law of thermodynamics allows full conversion of thermal energy.

• Thermal energy is always useful for work.

• Not all thermal energy can be converted into useful work.

• All thermal energy can be converted into useful work.

Heat can spontaneously flow from a colder body to a hotter body under certain conditions.

• Yes, under certain conditions like in refrigeration.

• Refrigeration does not allow heat to flow from cold to hot.

• Heat can only flow from hot to cold bodies.

• Heat flow is impossible without external work.

The efficiency of a Carnot engine depends only on the temperatures of the hot and cold reservoirs.

• The efficiency of a Carnot engine is constant regardless of temperature changes.

• The efficiency of a Carnot engine depends on the work done by the engine.

• True

• The efficiency of a Carnot engine is affected by the type of fuel used.

The work done by a heat pump is always greater than the heat it extracts from the cold reservoir.

• The heat pump only works in heating mode

• False

• The work done is equal to the heat extracted

• True