Physics for Scientists and Engineers
10th Edition
ISBN: 9781337553278
Author: Raymond A. Serway, John W. Jewett
Publisher: Cengage Learning
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Chapter 21, Problem 9P
If a 35.0% -efficient Carnot
Figure P21.2 Schematic representation of a heat engine.
Figure P21.4 Schematic representation of a heat pump.
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A particular power plant operates with a heat-source reservoir at 350°C and a heatsink reservoir at 30°C. It has a thermal efficiency equal to 55% of the Carnot-engine thermal efficiency for the same temperatures.
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efficiency of the plant to 35%? Again, η is 55% of the Carnot-engine value
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Chapter 21 Solutions
Physics for Scientists and Engineers
Ch. 21.1 - The energy input to an engine is 4.00 times...Ch. 21.2 - The energy entering an electric heater by...Ch. 21.4 - Three engines operate between reservoirs separated...Ch. 21.6 - (a) Suppose you select four cards at random from a...Ch. 21.7 - An ideal gas is taken from an initial temperature...Ch. 21.7 - True or False: The entropy change in an adiabatic...Ch. 21 - A particular heat engine has a mechanical power...Ch. 21 - The work done by an engine equals one-fourth the...Ch. 21 - Suppose a heat engine is connected to two energy...Ch. 21 - During each cycle, a refrigerator ejects 625 kJ of...
Ch. 21 - A freezer has a coefficient of performance of...Ch. 21 - A heat pump has a coefficient of performance equal...Ch. 21 - One of the most efficient heat engines ever built...Ch. 21 - Why is the following situation impossible? An...Ch. 21 - If a 35.0% -efficient Carnot heat engine (Fig....Ch. 21 - An ideal refrigerator or ideal heat pump is...Ch. 21 - A heat engine is being designed to have a Carnot...Ch. 21 - A power plant operates at a 32.0% efficiency...Ch. 21 - You are working on a summer job at a company that...Ch. 21 - A Carnot heat engine operates between temperatures...Ch. 21 - An electric generating station is designed to have...Ch. 21 - Suppose you build a two-engine device with the...Ch. 21 - A heat pump used for heating shown in Figure...Ch. 21 - A gasoline engine has a compression ratio of 6.00....Ch. 21 - An idealized diesel engine operates in a cycle...Ch. 21 - (a) Prepare a table like Table 21.1 for the...Ch. 21 - Prob. 21PCh. 21 - A Styrofoam cup holding 125 g of hot water at 100C...Ch. 21 - A 1 500-kg car is moving at 20.0 m/s. The driver...Ch. 21 - A 2.00-L container has a center partition that...Ch. 21 - Calculate the change in entropy of 250 g of water...Ch. 21 - What change in entropy occurs when a 27.9-g ice...Ch. 21 - When an aluminum bar is connected between a hot...Ch. 21 - When a metal bar is connected between a hot...Ch. 21 - How fast are you personally making the entropy of...Ch. 21 - Prob. 30APCh. 21 - The energy absorbed by an engine is three times...Ch. 21 - In 1993, the U.S. government instituted a...Ch. 21 - In 1816, Robert Stirling, a Scottish clergyman,...Ch. 21 - Suppose an ideal (Carnot) heat pump could be...Ch. 21 - Review. This problem complements Problem 44 in...Ch. 21 - A firebox is at 750 K, and the ambient temperature...Ch. 21 - A 1.00-mol sample of an ideal monatomic gas is...Ch. 21 - A system consisting of n moles of an ideal gas...Ch. 21 - A heat engine operates between two reservoirs at...Ch. 21 - You are working as an assistant to a physics...Ch. 21 - Prob. 41APCh. 21 - You are working as an expert witness for an...Ch. 21 - An athlete whose mass is 70.0 kg drinks 16.0...Ch. 21 - Prob. 44APCh. 21 - Prob. 45APCh. 21 - A sample consisting of n moles of an ideal gas...Ch. 21 - The compression ratio of an Otto cycle as shown in...
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- (a) What is the hot reservoir temperature of a Carnot engine that has an eficiency of 42.0% and a cold reservoir temperature of 210C ? (b) What must the hot reservoir temperature be for a real heat engine that achieves 0.700 of the maximum eficiency, but still has an efficiency of 42.0% (and a cold reservoir at 27.0C )? (c) Does your answer imply practical limits to the efficiency of car gasoline engines?arrow_forwardOf the following, which is not a statement of the second law of thermodynamics? (a) No heat engine operating in a cycle can absorb energy from a reservoir and use it entirely to do work, (b) No real engine operating between two energy reservoirs can be more efficient than a Carnot engine operating between the same two reservoirs, (c) When a system undergoes a change in state, the change in the internal energy of the system is the sum of the energy transferred to the system by heat and the work done on the system, (d) The entropy of the Universe increases in all natural processes, (e) Energy will not spontaneously transfer by heat from a cold object to a hot object.arrow_forwardUse a PV diagram such as the one in Figure 22.2 (page 653) to figure out how you could modify an engine to increase the work done.arrow_forward
- (a) What is the best coefficient of performance for a refrigerator that cools an environment at 30.0C and has heat transfer to another environment at 45.0C ? (b) How much work in joules must be done for a heat transfer of 4186 kJ from the cold environment? (c) What is the cost of doing this if the work costs 10.0 cents per 3.60106J (a kilowatthour)? (d) How many kJ of heat transfer occurs into the warm environment? (e) Discuss what type of refrigerator might operate between these temperatures.arrow_forward(a) On a winter day, a certain house loses 5.00108J of heat to the outside (about 500,000 Btu). What is the total change in entropy due to this heat transfer alone, assuming an average indoor temperature of 21.0C and an average outdoor temperature of 5.00C ? (b) This large change in entropy implies a large amount of energy has become unavailable to do work. Where do we find more energy when such energy is lost to us?arrow_forwardA sample of a monatomic ideal gas is contained in a cylinder with a piston. Its state is represented by the dot in the PV diagram shown in Figure OQ18.9. Arrows A through E represent isobaric, isothermal, adiabatic, and isovolumetric processes that the sample can undergo. In each process except D, the volume changes by a factor of 2. All five processes are reversible. Rank the processes according to the change in entropy of the gas from the largest positive value to the largest-magnitude negative value. In your rankings, display any cases of equality. Figure OQ18.9arrow_forward
- Figure P22.73 illustrates the cycle ABCA for a 2.00-mol sample of an ideal diatomic gas, where the process CA is a reversible isothermal expansion. What is a. the net work done by the gas during one cycle? b. How much energy is added to the gas by heat during one cycle? c. How much energy is exhausted from the gas by heat during one cycle? d. What is the efficiency of the cycle? e. What would be the efficiency of a Carnot engine operated between the temperatures at points A and B during each cycle?arrow_forward(a) In reaching equilibrium, how much heat transfer occurs from 1.00 kg of water at 40.0C when it is placed in contact with 1.00 kg of 20.0C water in reaching equilibrium? (b) What is the change in entropy due to this heat transfer? (c) How much work is made unavailable, taking the lowest temperature to be 20.0C ? Explicitly show how you follow the steps in the Problem-Solving Strategies for Entropy.arrow_forwardA heat pump has a coefficient of performance of 3.80 and operates with a power consumption of 7.03 103 W. (a) How much energy does it deliver into a home during 8.00 h of continuous operation? (b) How much energy does it extract from the outside air?arrow_forward
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