23. The Second Law of Thermodynamics

Heat Engines and the Second Law of Thermodynamics

phys2A ch15.7-8 The Second Law of Thermodynamics and Heat Engines

Introduction to Heat Engines

A heat engine exhausts <math display="inline"><mrow><mn>250</mn><mo rspace="thickmathspace">&#x2062;</mo><mi mathvariant="normal" class="MathML-Unit">J</mi></mrow></math> per cycle while doing <math display="inline"><mrow><mn>200</mn><mo rspace="thickmathspace">&#x2062;</mo><mi mathvariant="normal" class="MathML-Unit">J</mi></mrow></math> of work. What is the efficiency of this engine?

Your car’s engine can be modeled as a heat engine. How many joules must be extracted from your gas tank to get your <math display="inline"><mrow><mn>1200</mn><mo rspace="thickmathspace">&#x2062;</mo><mi mathvariant="normal" class="MathML-Unit">kg</mi></mrow></math> car to 26 m/s? Assume the thermal efficiency of your car is 16%. Ignore air resistance and other frictional effects on your car.

Lesson 8 - Heat Engines And 2nd Law of Thermodynamics (Physics Tutor)

 No, it violates the first law of thermodynamics. 

 No, it violates both the first and second laws of thermodynamics. 

 No, it violates the second law of thermodynamics. 

In each cycle, a heat engine absorbs <math display="inline"><mrow><mn>1200</mn><mo rspace="thickmathspace">&#x2062;</mo><mi mathvariant="normal" class="MathML-Unit">J</mi></mrow></math> from a 400°C hot reservoir, emits <math display="inline"><mrow><mn>600</mn><mo rspace="thickmathspace">&#x2062;</mo><mi mathvariant="normal" class="MathML-Unit">J</mi></mrow></math> to 80°C cold reservoir, while doing <math display="inline"><mrow><mn>600</mn><mo rspace="thickmathspace">&#x2062;</mo><mi mathvariant="normal" class="MathML-Unit">J</mi></mrow></math> of work. Is it physically possible for this engine to exist?

A diesel engine performs 2200 J of mechanical work and discards 4300 J of heat each cycle. (a) How much heat must be supplied to the engine in each cycle?

Efficiency of a Nuclear Power Plant

Second Law Thermodynamics, Heat Engines, Efficiency, Carnot Heat Engine

In each cycle, a heat engine absorbs <math display="inline"><mrow><mn>1200</mn><mo rspace="thickmathspace">&#x2062;</mo><mi mathvariant="normal" class="MathML-Unit">J</mi></mrow></math> from a 400°C hot reservoir, emits <math display="inline"><mrow><mn>700</mn><mo rspace="thickmathspace">&#x2062;</mo><mi mathvariant="normal" class="MathML-Unit">J</mi></mrow></math> to 80°C cold reservoir, while doing <math display="inline"><mrow><mn>500</mn><mo rspace="thickmathspace">&#x2062;</mo><mi mathvariant="normal" class="MathML-Unit">J</mi></mrow></math> of work. Is it physically possible for this engine to exist?

Power Output of a Gasoline Engine

A heat engine uses a tank of ice water as a cold reservoir. The engine takes in 8 kJ of heat from the hot reservoir, and the heat expelled melts 18g of ice in the tank. How much work does this engine do?

Thermal Efficiency & The Second Law of Thermodynamics

An aircraft engine takes in 9 kJ of heat and expels 6.4 kJ of heat each cycle. How much mechanical work does the engine do each cycle?

Heat Engines And Second Law Of Thermodynamics

A steam turbine takes in 75g of water and boils it as heat energy to run a 40% efficient engine. How much work does this engine do per cycle?

Heat engines and the 2nd law

First and Second Law of Thermodynamics and the Heat Engine

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