Thermodynamics and Engine Efficiency

In each cycle of a certain Carnot engine, 100 joules of heat is absorbed from the high‑temperature reservoir and 60 joules is exhausted to the low‑temperature reser­voir. What is the efficiency of the engine?

• 40%

• 60%

• 67%

• 150%

• 167%

A heat engine takes in 200 J of thermal energy and performs 50 J of work in each cycle. What is its efficiency?

• 50 %

• 40 %

• 25 %

• 20 %

• 12 %

The first law of thermodynamics states that the change in the internal energy of a system is equal to the difference in energy transferred to or from the system as heat and

• mass
• work done
• force
• pressure

Which best describes ENTROPY?

• Useful heat energy needed to drive an engine
• Heat that can be stored to be used at a later date
•   Random energy that escapes from the system
• A state of order in a physical system

Which state of H₂O  has the greatest entropy?

• Ice
• Water
• Vapor

As a system becomes more disordered, entropy

• remains the same
• increases
• decreases
• cannot be determined

The transfer of thermal energy between objects of different temperatures is called...

• temperature
• heat
• internal energy
• none of these

Heat transfer by conduction occurs when...

• particles bump into each other
• large numbers of atoms move from place to place
• atoms give off heat in the form of electromagnetic waves
• electromagnetic waves travel from place to place through a vacuum

Heat transfer by convection occurs when...

• electrons bump into other electrons
• large numbers of atoms move from place to place
• atoms give off heat in the form of electromagnetic waves
• electromagnetic waves travel from place to place through a vacuum

Heat travels from the sun to the earth by the process of...

• conduction
• convection
• radiation
• insulation