lilernoEngineeringOpening Lilerno
Chapter 14 · Guided self-study
Intro + external course studyMake an energy balance and distinguish energy conservation from useful work.
Build the idea
An original introduction, worked example and practice, followed by a curated reading sequence. The external courses supply deeper teaching and problem sets.
This guide is an orientation, not a complete university module. Practical work needs suitable facilities, safety review and supervision.
Start with these prerequisites
Shared science foundations
Thermodynamics accounts for energy and constrains what energy conversions are possible. Start by drawing the system boundary and declaring a sign convention.
Module lens
Heat and work are transfers; internal energy records what remains stored in the selected system.
Internal energy is a state property. Heat and work describe transfer across a boundary, not substances stored inside the system. For a closed system with negligible kinetic and potential energy change, ΔU = Q − W when work out is positive.
The first law conserves energy. The second law constrains direction and useful work: entropy generation is nonnegative. A heat engine's efficiency uses net work output divided by heat input, not total energy passing through every component.
See the relationship
Change one quantity, watch the graph respond, then explain the result in your own words.
Predict → change → explain
Can internal energy fall even while heat enters?
Axes: Work out (J) → Internal energy change (J). Bounds may rescale when inputs change.
800 J in − 300 J out = 500 J stored change. Negative ΔU means internal energy decreases.
Closed system; heat into the system and work out are positive. Changes in kinetic and potential energy are neglected.
Original Lilerno illustration. Inputs are illustrative; this is not experimental evidence or a design rating.
| Series | Work out (J) | Internal energy change (J) |
|---|---|---|
| ΔU = Q − W | 0 | 800 |
| ΔU = Q − W | 18.75 | 781.3 |
| ΔU = Q − W | 37.5 | 762.5 |
| ΔU = Q − W | 56.25 | 743.8 |
| ΔU = Q − W | 75 | 725 |
| ΔU = Q − W | 93.75 | 706.3 |
| ΔU = Q − W | 112.5 | 687.5 |
| ΔU = Q − W | 131.3 | 668.8 |
| ΔU = Q − W | 150 | 650 |
| ΔU = Q − W | 168.8 | 631.3 |
| ΔU = Q − W | 187.5 | 612.5 |
| ΔU = Q − W | 206.3 | 593.8 |
| ΔU = Q − W | 225 | 575 |
| ΔU = Q − W | 243.8 | 556.3 |
| ΔU = Q − W | 262.5 | 537.5 |
| ΔU = Q − W | 281.3 | 518.8 |
| ΔU = Q − W | 300 | 500 |
| ΔU = Q − W | 318.8 | 481.3 |
| ΔU = Q − W | 337.5 | 462.5 |
| ΔU = Q − W | 356.3 | 443.8 |
| ΔU = Q − W | 375 | 425 |
| ΔU = Q − W | 393.8 | 406.3 |
| ΔU = Q − W | 412.5 | 387.5 |
| ΔU = Q − W | 431.3 | 368.8 |
| ΔU = Q − W | 450 | 350 |
| ΔU = Q − W | 468.8 | 331.3 |
| ΔU = Q − W | 487.5 | 312.5 |
| ΔU = Q − W | 506.3 | 293.8 |
| ΔU = Q − W | 525 | 275 |
| ΔU = Q − W | 543.8 | 256.3 |
| ΔU = Q − W | 562.5 | 237.5 |
| ΔU = Q − W | 581.3 | 218.8 |
| ΔU = Q − W | 600 | 200 |
| ΔU = Q − W | 618.8 | 181.3 |
| ΔU = Q − W | 637.5 | 162.5 |
| ΔU = Q − W | 656.3 | 143.8 |
| ΔU = Q − W | 675 | 125 |
| ΔU = Q − W | 693.8 | 106.3 |
| ΔU = Q − W | 712.5 | 87.5 |
| ΔU = Q − W | 731.3 | 68.75 |
| ΔU = Q − W | 750 | 50 |
| ΔU = Q − W | 768.8 | 31.25 |
| ΔU = Q − W | 787.5 | 12.5 |
| ΔU = Q − W | 806.3 | -6.25 |
| ΔU = Q − W | 825 | -25 |
| ΔU = Q − W | 843.8 | -43.75 |
| ΔU = Q − W | 862.5 | -62.5 |
| ΔU = Q − W | 881.3 | -81.25 |
| ΔU = Q − W | 900 | -100 |
| ΔU = Q − W | 918.8 | -118.8 |
| ΔU = Q − W | 937.5 | -137.5 |
| ΔU = Q − W | 956.3 | -156.3 |
| ΔU = Q − W | 975 | -175 |
| ΔU = Q − W | 993.8 | -193.8 |
| ΔU = Q − W | 1013 | -212.5 |
| ΔU = Q − W | 1031 | -231.3 |
| ΔU = Q − W | 1050 | -250 |
| ΔU = Q − W | 1069 | -268.8 |
| ΔU = Q − W | 1088 | -287.5 |
| ΔU = Q − W | 1106 | -306.3 |
| ΔU = Q − W | 1125 | -325 |
| ΔU = Q − W | 1144 | -343.8 |
| ΔU = Q − W | 1163 | -362.5 |
| ΔU = Q − W | 1181 | -381.3 |
| ΔU = Q − W | 1200 | -400 |
| ΔU = Q − W | 1219 | -418.8 |
| ΔU = Q − W | 1238 | -437.5 |
| ΔU = Q − W | 1256 | -456.3 |
| ΔU = Q − W | 1275 | -475 |
| ΔU = Q − W | 1294 | -493.8 |
| ΔU = Q − W | 1313 | -512.5 |
| ΔU = Q − W | 1331 | -531.3 |
| ΔU = Q − W | 1350 | -550 |
| ΔU = Q − W | 1369 | -568.8 |
| ΔU = Q − W | 1388 | -587.5 |
| ΔU = Q − W | 1406 | -606.3 |
| ΔU = Q − W | 1425 | -625 |
| ΔU = Q − W | 1444 | -643.8 |
| ΔU = Q − W | 1463 | -662.5 |
| ΔU = Q − W | 1481 | -681.3 |
| ΔU = Q − W | 1500 | -700 |
| Chosen balance | 300 | 500 |
Save your place when you finish reading.
Original Lilerno example
A closed system receives 500 J of heat and performs 200 J of work; kinetic and potential changes are negligible.
Declare Q positive into the system and W positive out.
Apply ΔU = Q − W.
ΔU = 500 − 200 = 300 J.
Test the model
Open learning, traceable sources
Work in this order. These links open the publisher’s material; free access does not always permit republication.
MIT OpenCourseWare
Start with: Fundamentals → second law → power cycles
Work through lecture notes, recitations and assignments. Draw a boundary for every balance.
Recall, then record
Close the explanation and answer these in your own words. Return tomorrow, then again later in the week.
Is mass crossing the boundary?
Which work sign convention?
What does the second law add?
Draw an energy-flow diagram for an everyday device. Separate measured inputs from assumptions; do not open or modify the device.
Self-reported tasks, not an assessment of mastery or university credit. Reading a page does not complete a chapter.
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Open learning, traceable sources
Original Lilerno lessons and diagrams, supported by these references. Free access does not always permit republication. Links open the publisher’s material.
Thermodynamic foundations, second law, power cycles and heat transfer. Aerospace examples share the mechanical-engineering energy principles.
CC BY-NC-SA 4.0 except separately credited material. Linked for external study, not reproduced. Some assigned textbooks/software require separate access.
Open source ↗Rights / publisher record ↗