Exam 12: Thermodynamics

We say that energy cannot be created nor destroyed, yet a heat pump usually delivers more energy (heat) into the house than it receives from the power source (electricity, gas, etc). Why is this not a violation of the law of conservation of energy?

A coal-fired plant generates 600 MW of electric power. The plant uses 4.8 × 10⁶ kg of coal each day. The heat of combustion of coal is 3.3 × 10⁷ J/kg. The steam that drives the turbines is at a temperature of 300°C, and the exhaust water is at 37°C. How much thermal energy is wasted each day?

An ideal gas is compressed to one-half its original volume during an isothermal process. The final pressure of the gas

Thermal efficiency (non-Carnot) is

The change in entropy is Q/T for

A reversible engine takes in 40. Joules of heat, does 10. J of work, and expels 30. J of wasted heat during each cycle. If it is operated in reverse as a refrigerator, then its COP would be

A heat engine operating between 40° C and 380° C has an efficiency 60% of that of a Carnot engine operating between the same temperatures. If the engine absorbs heat at a rate of 60 kW, at what rate does it exhaust heat?

Entropy of the universe is increasing.

A cyclic process is carried out on an ideal gas such that it returns to its initial State at the end of a cycle. If the process was carried out on a clockwise sense around the enclosed area, as shown on the p-V diagram in Figure 12-4, then that area represents

A certain amount of a 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?

The process shown on the T-V graph in Figure 12-8 is an

Is it possible for heat to travel from a cold object to a hotter object?

An ideal gas is compressed isothermally from 30 L to 20 L. During this process, 6 J of energy is expended by the external mechanism that compressed the gas. What is the change of internal energy for this gas?

A coal-fired plant generates 600 MW of electric power. The plant uses 4.8 × 10⁶ kg of coal each day. The heat of combustion of coal is 3.3 × 10⁷ J/kg. The steam that drives the turbines is at a temperature of 300°C, and the exhaust water is at 37°C. (a) What is the overall efficiency of the plant for generating electric power? (b) What is the Carnot efficiency?

Coefficient of performance is

Isobaric work is

A cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of a cycle. If the process was carried out in a clockwise sense around the enclosed area, as shown on the p-V diagram in Figure 12-2, then the change of internal energy over the full cycle

The Otto cycle has how many strokes per cycle during which the volume decreases?

The work done by the gas is zero during an

The Department of Energy develops a new reversible engine which has a COP of 4 when operated as a refrigerator and a COP of 5 when operated as a heat pump. What is its efficiency when operated as an engine doing work?