Physics for Scientists and Engineers with Modern Physics
4th Edition
ISBN: 9780131495081
Author: Douglas C. Giancoli
Publisher: Addison-Wesley
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Chapter 20, Problem 76GP
To determine
The electrical power saved in the ideal air conditioner.
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Students have asked these similar questions
(1) An incandescent light bulb produces 5.85 Joules of light energy each second. This bulb is 7.80%
efficient, meaning that only 7.80% the total energy it consumes becomes light and the rest becomes waste
heat. A 12.0 W fluorescent bulb is designed to produce the same illumination (in Joules of light energy
per second) as the incandescent bulb. A large building uses 17,530 light bulbs. At a cost of 8.56€/kW-hr
for electricity, how much money will the owners of the building save each year if they use fluorescent
bulbs instead of incandescent bulbs? Express your answer in dollars. [answer: about $828,000]
An incandescent lightbulb is an inexpensive but highly inefficient device that converts electrical energy into light. It converts about 10 percent of the electrical energy it consumes into light while converting the remaining 90 percent into heat. The glass bulb of the lamp heats up very quickly as a result of absorbing all that heat and dissipating it to the surroundings by convection and radiation. Consider an 8-cm-diameter 60-W lightbulb in a room at 25°C. The emissivity of the glass is 0.9. Assuming that 10 percent of the energy passes through the glass bulb as light with negligible absorption and the rest of the energy is absorbed and dissipated by the bulb itself by natural convection and radiation, determine the equilibrium temperature of the glass bulb. Assume the interior surfaces of the room to be at room temperature.
To heat a room with dimensions width a=3 m, length b=5 m, height h=2,2 m, approximately an electrical power of P=10 W per square meter is needed. At a cost of 0.2 soles per kW.h, how much will it cost per day to use this heater?
Chapter 20 Solutions
Physics for Scientists and Engineers with Modern Physics
Ch. 20.2 - An adiabatic process is defined as one in which no...Ch. 20.3 - A motor is running with an intake temperature TH =...Ch. 20.6 - A 1.00.kg piece of ice at 0C melts very slowly to...Ch. 20.9 - Prob. 1EECh. 20 - Prob. 1QCh. 20 - Can you warm a kitchen in winter by leaving the...Ch. 20 - Would a definition of heat engine efficiency as e...Ch. 20 - What plays the role of high-temperature and...Ch. 20 - Which will give the greater improvement in the...Ch. 20 - The oceans contain a tremendous amount of thermal...
Ch. 20 - Discuss the factors that keep real engines from...Ch. 20 - Prob. 8QCh. 20 - Describe a process in nature that is nearly...Ch. 20 - (a) Describe how heat could be added to a system...Ch. 20 - Suppose a gas expands to twice its original volume...Ch. 20 - Give three examples, other than those mentioned in...Ch. 20 - Which do you think has the greater entropy, 1 kg...Ch. 20 - (a) What happens if you remove the lid of a bottle...Ch. 20 - Prob. 15QCh. 20 - Prob. 16QCh. 20 - Prob. 17QCh. 20 - The first law of thermodynamics is sometimes...Ch. 20 - Powdered milk is very slowly (quasistatically)...Ch. 20 - Two identical systems are taken from state a to...Ch. 20 - It can he said that the total change in entropy...Ch. 20 - Use arguments, other than the principle of entropy...Ch. 20 - (I) A heat engine exhausts 7800 J of heat while...Ch. 20 - (I) A certain power plant puts out 580 MW of...Ch. 20 - (II) A typical compact car experiences a total...Ch. 20 - (II) A four-cylinder gasoline engine has an...Ch. 20 - (II) The burning of gasoline in a car releases...Ch. 20 - (II) Figure 2017 is a PV diagram for a reversible...Ch. 20 - (III) The operation of a diesel engine can be...Ch. 20 - (I) What is the maximum efficiency of a heat...Ch. 20 - (I) It is not necessary that a heat engines hot...Ch. 20 - (II) A heal engine exhausts its heat at 340C and...Ch. 20 - (II) (a) Show that the work done by a Carnot...Ch. 20 - (II) A Carnot engines operating temperatures are...Ch. 20 - (II) A nuclear power plant operates at 65% of its...Ch. 20 - (II) A Carnot engine performs work at the rate of...Ch. 20 - (II) Assume that a 65 kg hiker needs 4.0 103 kcal...Ch. 20 - (II) A particular car does work at the rate of...Ch. 20 - (II) A heat engine utilizes a heat source at 580C...Ch. 20 - (II) The working substance of a certain Carnot...Ch. 20 - (III) A Carnot cycle, shown in Fig. 20-7, has the...Ch. 20 - (III) One mole of monatomic gas undergoes a Carnot...Ch. 20 - (III) In an engine that approximates the Otto...Ch. 20 - (I) If an ideal refrigerator keeps its contents at...Ch. 20 - (I) The low temperature of a freezer cooling coil...Ch. 20 - (II) An ideal (Carnot) engine has an efficiency of...Ch. 20 - (II) An ideal heal pump is used to maintain the...Ch. 20 - (II) A restaurant refrigerator has a coefficient...Ch. 20 - (II) A heat pump is used to keep a house warm at...Ch. 20 - (II) (a) Given that the coefficient of performance...Ch. 20 - (II) A Carnot refrigerator (reverse of a Carnot...Ch. 20 - (II) A central heat pump updating as an air...Ch. 20 - (II) What volume of water at 0C can a freezer make...Ch. 20 - (I) What is the change in entropy of 250g of steam...Ch. 20 - (I) A 7.5-kg box having an initial speed of 4.0m/s...Ch. 20 - (I) What is the change in entropy of 1.00 m3 of...Ch. 20 - (II) If 1.00m3 of water at 0C is frozen and cooled...Ch. 20 - (II) If 0.45kg f water at 100C is changed by a...Ch. 20 - (II) An aluminum rod conducts 9.50 cal/s from a...Ch. 20 - (II) A 2.8-kg piece of aluminum at 43.0C is placed...Ch. 20 - (II) An ideal gas expands isothermally (T = 410 K)...Ch. 20 - (II) When 2.0 kg of water at 12.0C is mixed with...Ch. 20 - (II) (a) An ice cube of mass m at 0C is placed in...Ch. 20 - (II) The temperature of 2.0mol of an ideal...Ch. 20 - (II) Calculate the change in entropy of 1.00kg of...Ch. 20 - (II) An ideal gas of n moles undergoes the...Ch. 20 - (II) Two samples of an ideal gas are initially at...Ch. 20 - (II) A 150-g insulated aluminum cup at 15C is...Ch. 20 - (II) (a) Why would you expect the total entropy...Ch. 20 - (II) 1.00 mole of nitrogen (N2) gas and 1.00 mole...Ch. 20 - (II) Thermodynamic processes are sometimes...Ch. 20 - (III) The specific heat per mole of potassium at...Ch. 20 - (III) Consider an ideal gas of n moles with molar...Ch. 20 - (III) A general theorem states that the amount of...Ch. 20 - (III) Determine the work available in a 3.5-kg...Ch. 20 - (I) Use Eq. 2014 to determine the entropy of each...Ch. 20 - (II) Suppose that you repeatedly shake six coins...Ch. 20 - (II) Calculate the relative probabilities, when...Ch. 20 - (II) (a) Suppose you have four coins, all with...Ch. 20 - Prob. 58PCh. 20 - (II) Energy may be stored for use during peak...Ch. 20 - (II) Solar cells (Fig. 20-22) can produce about...Ch. 20 - Prob. 61PCh. 20 - It has been suggested that a heat engine could be...Ch. 20 - A heat engine takes a diatomic gas around the...Ch. 20 - A 126.5-g insulated aluminum cup at 18.00C is...Ch. 20 - (a) At a steam power plant, steam engines work in...Ch. 20 - (II) Refrigeration units can be rated in tons. A...Ch. 20 - Prob. 67GPCh. 20 - (a) What is the coefficient of performance of an...Ch. 20 - The operation of a certain heat engine takes an...Ch. 20 - A car engine whose output power is 155 hp operates...Ch. 20 - Suppose a power plant delivers energy at 850 MW...Ch. 20 - 1.00 mole of an ideal monatomic gas at STP first...Ch. 20 - Two 1100-kg cars are traveling 75 km/h in opposite...Ch. 20 - Metabolizing 1.0 kg of fat results in about 3.7 ...Ch. 20 - A cooling unit for a new freezer has an inner...Ch. 20 - Prob. 76GPCh. 20 - The Stirling cycle shown in Fig 20-27, is useful...Ch. 20 - A gas turbine operates under the Brayton cycle,...Ch. 20 - Thermodynamic processes can be represented not...Ch. 20 - An aluminum can, with negligible heat capacity, is...Ch. 20 - Prob. 81GPCh. 20 - A bowl contains a large number of red, orange, and...
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