The efficiency of a particular car engine is 25% when the engine does 8.2 kJ of work per cycle. Assume the process is reversible. What are (a) the energy the engine gains per cycle as heat Qgain from the fuel combustion and (b) the energy the engine loses per cycle as heat Qlost? If a tune-up increases the efficiency to 31%, what are (c)Qgain and (d) Qlost at the same work value?

The efficiency of a particular car engine is 25% when the engine does 8.2 kJ of work per cycle. Assume the process is reversible. What are (a) the energy the engine gains per cycle as heat Qgain from the fuel combustion and (b) the energy the engine loses per cycle as heat Qlost? If a tune-up increases the efficiency to 31%, what are (c)Qgain and (d) Qlost at the same work value?

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter4: The Second Law Of Thermodynamics

Section: Chapter Questions

Problem 31P: If a refrigerator discards 80 J of heat per cycle and its coefficient of performance is 6.0, what...

See similar textbooks

Similar questions

A multicylinder gasoline engine in an airplane, operating at 2.50 103 rev/min, takes in energy 7.89 103 J and exhausts 4.58 103 J for each revolution of the crankshaft. (a) How many liters of fuel does it consume in 1.00 h of operation if the heat of combustion of the fuel is equal to 4.03 107 J/L? (b) What is the mechanical power output of the engine? Ignore friction and express the answer in horsepower. (c) What is the torque exerted by the crankshaft on the load? (d) What power must the exhaust and cooling system transfer out of the engine?
Consider a transformation from point A to B in a two-step process. First, the pressure is lowered from 3 MPa at point A to a pressure of 1 MPa, while keeping the volume at 2 L by cooling the system. The state reached is labeled C. Then the system is heated at a constant pressure to reach a volume of 6 L in the state B. (a) Find the amount of work on the ACB path. (b) Find the amount of heat exchanged by the system when it goes from A to B on the ACB path. (c) the change in the internal energy when the AB process occurs adiabatically with the AB change though the two-step process on the ACB path.
A Carnot engine employs 1.5 mol of nitrogen gas as a working substance, which is considered as an ideal diatomic gas with =7.5 at the working temperatures of the engine. The Carnot cycle goes in the cycle ABCDA with AB being an isothermal expansion. The volume at points A and C of the cycle are 5.0103 m3 and 0.15 L, respectively. The engine operates between two thermal baths of temperature 500 K 300 K. (a) Find the values of volume at B and D. (b) How much heat is absorbed by the gas in the AB isothermal expansion? (c) How much work is done by the gas in the AB isothermal expansion? (d) How much heat is given up by the gas in the CD isothermal expansion? (e) How much work is done by the gas in the CD isothermal compression? (f) How much work is done by the gas in the BC adiabatic expansion? (g) How much work is done by the gas in the DA adiabatic compression? (h) Find the value of efficiency of the engine based on the net and heat input. Compare this value to the efficiency of a Carnot engine based on the temperatures of the baths.
An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 95 kPa and 27C, and 750 kJ/kg of heat is transferred to air during the constant-volume heat-addition process. Taking into account the variation of specific heats with temperature, determine (a) the pressure and temperature at the end of the heat- addition process, (b) the net work output, (c) the thermal efficiency, and (d) the mean effective pressure for the cycle.
A Carnot refrigerator extracts 35.0 kJ as heat during each cycle, operating with a coefficient of performance of 4.60. What are (a) the energy per cycle transferred as heat to the room and (b) the work done per cycle?
An engine that absorbs 480 J of heat per cycle has an efficiency of 00.34. How much work W does the engine do in a cycle?
A four-cylinder spark-ignition engine has a compression ratio of 10.5, and each cylinder has a maximum volume of 0.4 L. At the beginning of the compression process, the air is at 98 kPa and 37C, and the maximum temperature in the cycle is 2100 K. Assuming the engine to operate on the ideal Otto cycle, determine (a) the amount of heat supplied per cylinder, (b) the thermal efficiency, and (c) the number of revolutions per minute required for a net power output of 45 kW. Assume variable specific heats for air.
What is the efficiency of a gasoline engine that receives 194.5 J of energy from combustion and loses 143.4 J by heat to the exhaust during one cycle?
An engine with an efficiency of 0.34 absorbs 55 J from a heat reservoir in each cycle. If it undergoes 221 cycles per minute, what is the power output in watts?
A diesel engine performs 2200 J of mechanical work and discards 4300 J of heat each cycle. How much heat much be supplied to engine in each cycle? and what is the thermal efficiency of the engine?
A nuclear power plant operates at 70 % of its maximum theoretical (Carnot) efficiency between temperatures of 620 ∘C and 330 ∘C. If the plant produces electric energy at the rate of 1.5 GW , how much exhaust heat is discharged per hour? Answer must be given in J/h
A nuclear power plant operates at 66 % of its maximum theoretical (Carnot) efficiency between temperatures of 630 ∘C and 390 ∘C. If the plant produces electric energy at the rate of 1.0 GW , how much exhaust heat is discharged per hour? Express your answer using two significant figures.