QUICK REVIEW
Quick Review — First Law of Thermodynamics — Calculus-Based
Refresh the essential ideas and relationships for First Law of Thermodynamics in just a few minutes.
TIME
5–10 minutes
BEST FOR
A rapid refresh
FINISH WITH
Key ideas refreshed
After this quick review, you'll be able to...
recall the essential ideas and decide what to review next.
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Course Alignment
This Physics Sensei Unit Review is an independent learning resource. Use it to reinforce key concepts, prepare for homework, or review before a quiz or exam.
RESOURCE: Physics Sensei Unit Review | UNIT ID: THM-U08 | TOPIC: First Law of Thermodynamics | COURSE LEVEL: Calculus-Based
BEST USED ✓ After learning the unit ✓ Before starting homework ✓ Before a quiz or exam
Your Review Plan
Complete these four stages to quickly refresh the essential ideas and confirm you're ready to continue.
4 Stages • Approximately 5–10 minutes.
Quick Recall
Let's quickly refresh what you already know. These short recall activities will help you bring the most important ideas back to mind before reviewing them.
QUICK RECALL
Recall Activity
Complete the three statements from memory before revealing the answer.
Differential form: Write the first law for an infinitesimal change using the work-by-system convention.
Reveal Answers
dU = δQ - δW.
Why it works: U is a state function, while heat and work are path-dependent transfers.
Ready to refresh the essentials?
Great! Now let's review the most important ideas you'll want to remember.
Essential Idea
Take one last look at the most important concept from this unit. If you remember this idea, the rest will come back much more easily.
ESSENTIAL IDEA
First Law and Exact Differentials
For the work-by-system convention, dU = δQ - δW and over a finite process ΔU = Q - W. Because U is a state function, dU is exact; heat and work are process-dependent and are commonly written with inexact differentials.
dU = δQ − δW and ΔU = Q − W
Example: For a complete cycle, ΔU = 0, so net Q equals net W.
Sensei note: Keep the sign convention fixed throughout a derivation.
Ready to check your memory?
You've refreshed the essential idea. Now see how much you remember before moving on. Need a quick reminder?
Confidence Check
You've refreshed the essential ideas. Now answer this quick confidence check to confirm you're ready to move on.
CONFIDENCE CHECK
Cycle relation
Answer all three without notes.
Solve using the first law and the stated sign convention. For a complete cycle, what relation connects net heat and net work?
Reveal Answers
net Q = net W.
Why it works: Because ΔU for the cycle = 0.
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Next Step
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