Exam 21: Degradation of Energy

The temperature inside a Carnot refrigerator placed in a kitchen at 22.0°C is 2.0°C.The heat extracted from the refrigerator is 89 MJ/h.What power is needed to operate this refrigerator?

An air conditioner with a coefficient of performance of 3.5 uses 30 kW of power.How much power is it discharging to the outdoors?

The second law of thermodynamics leads us to conclude that

A certain engine extracts 1300 J of heat from a hot temperature reservoir and discharges 700 J of heat to a cold temperature reservoir.What is the efficiency of this engine?

A Carnot refrigerator takes heat from water at 0°C and rejects heat to a room at 12°C.Suppose that 92.0 grams of water at 0°C are converted to ice at 0°C by the refrigerator.Calculate the mechanical energy that must be supplied to the refrigerator.The heat of fusion of water is 3.34 × 10⁵ J/kg.

One of the most efficient engines built so far has the following characteristics: combustion chamber temperature = 1900°C exhaust temperature = 430°C 7.0 × 10⁹ cal of fuel produces 1.4 × 10¹⁰ J of work in one hour,where 1 cal = 4.19 J (a)What is the actual efficiency of this engine? (b)What is the Carnot efficiency of the engine? (c)What is the power output of this engine?

A system consists of two very large thermal reservoirs in contact with each other,one at temperature 300°C and the other at temperature 200°C. When 600 J of heat transfers from the 300°C reservoir to the 200°C reservoir,what is the change in entropy of this system?

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 engine operates between a high temperature reservoir at 435 K and a river with water at 280 K.If it absorbs 3700 J of heat each cycle,how much work per cycle does it perform?

A Carnot cycle engine operates between a low temperature reservoir at 20°C and a high temperature reservoir at 800°C. If the engine is required to output 20.0 kJ of work per cycle,how much heat must the high temperature reservoir transfer to the engine during each cycle?

A perfect Carnot engine operates between the temperatures of 300K and 700K,drawing 60 kJ of heat from the 700K reservoir in each cycle.How much heat is dumped into the 300K reservoir in each cycle?

A Carnot engine is operated as a heat pump to heat a room in the winter. The heat pump delivers heat to the room at the rate of 34 kJ per second and maintains the room at a temperature of 293 K when the outside temperature is 229 K.The power requirement for the heat pump under these operating conditions is closest to

A nuclear fission power plant has an actual efficiency of 39%.If 0.25 MW of power are produced by the nuclear fission,how much electric power does the power plant output?

A coal-fired plant generates 600 MW of electric power. The plant uses 4.8 × 10⁶ kg of coal each day. The heat produced by the 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 maximum efficiency that this plant could possibly have using the same temperature extremes that it presently uses? (c)How much thermal energy is exhausted each day by this plant?

An ice cube at 0°C is placed in a very large bathtub filled with water at 30°C and allowed to melt,causing no appreciable change in the temperature of the bath water.Which one of the following statements is true?

You want to design an ideal Carnot heat engine that wastes only 35.0% of the heat that goes into it.The lowest cold-reservoir temperature available to you is +15.0°C.If 150.0 J of work is done per cycle,the heat input per cycle is closest to

As a result of any natural process,the total entropy of any system plus that of its environment

A Carnot air conditioner operates between an indoor temperature of 20°C and an outdoor temperature of 39°C.How much energy does it need to remove 2000 J of heat from the interior of the house?

A hot piece of iron is thrown into the ocean and its temperature eventually stabilizes.Which of the following statements concerning this process is correct? (There may be more than one correct choice.)