Skip to ContentGo to accessibility pageKeyboard shortcuts menu
OpenStax Logo
Physics

Problems

PhysicsProblems

Problems

12.2 First law of Thermodynamics: Thermal Energy and Work

25 .
Some amount of energy is transferred by heat into a system. The net work done by the system is 50 J , while the increase in its internal energy is 30 J . What is the amount of net heat?
  1. − 80 J
  2. − 20 J
  3. 20 J
  4. 80 J
26 .
Eighty joules are added by heat to a system, while it does 20 J of work. Later, 30 J are added by heat to the system, and it does 40 J of work. What is the change in the system’s internal energy?
  1. 30 J
  2. 50 J
  3. 60 J
  4. 110 J

12.4 Applications of Thermodynamics: Heat Engines, Heat Pumps, and Refrigerators

27.

A coal power station functions at 40.0 percent efficiency. What is the amount of work it does if it takes in 1.20×1012 J by heat?

  1. 3×1010 J
  2. 4.8×1011 J
  3. 3×1012 J
  4. 4.8×1013 J
28.

A heat engine functions with 70.7 percent thermal efficiency and consumes 12.0 kJ from heat daily. If its efficiency were raised to 75.0 percent, how much energy from heat would be saved daily, while providing the same output?

  1. −10.8 kJ
  2. −1.08 kJ
  3. 0.7 kJ
  4. 7 kJ
PreviousNext
Order a print copy
Citation/Attribution

This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute Texas Education Agency (TEA). The original material is available at: https://www.texasgateway.org/book/tea-physics . Changes were made to the original material, including updates to art, structure, and other content updates.

Attribution information
  • If you are redistributing all or part of this book in a print format, then you must include on every physical page the following attribution:
    Access for free at https://openstax.org/books/physics/pages/1-introduction
  • If you are redistributing all or part of this book in a digital format, then you must include on every digital page view the following attribution:
    Access for free at https://openstax.org/books/physics/pages/1-introduction
Citation information

© Jun 7, 2024 Texas Education Agency (TEA). The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.