Exam 11: Using Energy

An ideal Carnot engine extracts 529 J of heat from a high-temperature reservoir during each cycle, and rejects $225 \mathrm {~J}$ of heat to a low-temperature reservoir during the same cycle. What is the efficiency of the engine?

A fixed amount of an ideal monatomic gas is maintained at constant volume as it is cooled by 50 K. This feat is accomplished by removing 400 J of energy from the gas. How much work is done by the gas during this process?

For a certain ideal Carnot engine, the hot reservoir is 35 C° higher than the cold reservoir. If this engine is to have an efficiency of 20%, what must be the temperature of the hot reservoir?

The second law of thermodynamics leads us to conclude that

A compression, at a constant pressure of 140 kPa, is performed on 4.0 moles of an ideal monatomic gas for which C_V = 3/2 R. The compression reduces the volume of the gas from $0.26 \mathrm {~m} ^ { 3 }$ to $0.12 \mathrm {~m} ^ { 3 }$ What is the change in the internal (thermal)energy of the gas during this process? (R = 8.31 J/mol ? K)

If the efficiency of a reversible engine is 28%, what is its COP (performance coefficient)operated (a)as a refrigerator, and (b)as a heat pump?

In an isochoric process, the internal (thermal)energy of a gas decreases by 50 J. How much work is done by the gas during this process?

Which of the following is a false statement?

An air conditioner with a coefficient of performance of 3.50 uses 30.0 kW of power to operate. What power is it discharging to the outdoors?

A cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of a cycle, as shown in the pV diagram in the figure. If the process is carried out in a clockwise sense around the enclosed area, as shown on the figure, then the change of internal energy over the full cycle

An ideal Carnot heat engine operates between $285 \mathrm {~K}$ and $460 \mathrm {~K}$ What is its efficiency?

The figure shows a pV diagram for a gas going through a cycle from A to B to C and back to A. From point A to point B, the gas absorbs 50 J of heat and finds its internal (thermal)energy has increased by 20 J. Going from B to C, the internal (thermal)energy decreases by 5.0 J. (a)How much work was done by the gas from A to B? (b)How much heat was absorbed by the gas from B to C? (c)How much work was done by the gas going from B to C?

An ideal Carnot engine is operated as an air conditioner to cool a house in the summer. The air conditioner removes $14 \mathrm {~kJ}$ of heat per second from the house, and maintains the inside temperature at $293 \mathrm {~K}$ while the outside temperature is $369 \mathrm {~K} .$ The power required to run the air conditioner under these operating conditions is closest to

At what, if any, temperature are the numerical readings on the Fahrenheit and Celsius scales the same?

An ideal Carnot heat engine has an efficiency of 0.600. If it operates between a deep lake with a constant temperature of $294.0 \mathrm {~K}$ and a hot reservoir, what is the temperature of the hot reservoir?

A heat engine with an efficiency of 30% performs 2500 J of work. How much heat is discharged to the lower temperature reservoir?

A cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of a cycle, as shown in the pV diagram in the figure. If the process is carried out in a counter-clockwise sense around the enclosed area, as shown on the figure, then the magnitude of the enclosed area represents

During each cycle of operation, a refrigerator absorbs 230 J of heat from the freezer and expels 356 J of heat to the room. How much work input is required in each cycle?

A Carnot cycle consists of

A heat engine having the maximum possible efficiency has an efficiency of 25% when operating between two heat reservoirs. If the temperature of the cold reservoir is 300 K, what is the temperature of the hot reservoir?