First Law: Closed SystemHeat in, work out, and the internal energy left over, with the sign rule.Mechanical EngineeringHeat added minus work done by the system equalsthe rise in its internal energy.ΔU = Q − W · per unit mass: Δu = q − wQ = 500 J, W = 200 JΔU = 300 JThe gas heats up.Adiabatic compressionΔU = −WQ = 0, W negative.Rigid vessel heatedQ = m cv ΔTNo boundary work.THE COMMON MISTAKE✗ Taking W as work done on the system✓ W is work done BY the systemIn the engineering convention heat in and work out are positive. Mixing it withthe chemistry convention flips the sign of every answer.Applies to a fixed mass with no flow across the boundary. Flow devicesneed the steady-flow form.First Law: Closed Systemlearnposters.com
First Law: Closed System — printable engineering wall chart from LearnPosters. Free vector PDF, US Letter and A4.

What’s on the First Law: Closed System poster

The rule, 3 worked examples, and the mistake everyone makes.

Applies to a fixed mass with no flow across the boundary. Flow devices need the steady-flow form.

Questions about the First Law: Closed System poster

What’s on the First Law: Closed System poster?
The rule, 3 worked examples, and the mistake everyone makes. Heat added minus work done by the system equals the rise in its internal energy.; ΔU = Q − W · per unit mass: Δu = q − w; Q = 500 J, W = 200 J = ΔU = 300 J; Adiabatic compression = ΔU = −W; Rigid vessel heated = Q = m cv ΔT; Common mistake: Taking W as work done on the system → W is work done BY the system. Applies to a fixed mass with no flow across the boundary. Flow devices need the steady-flow form.
Who is the First Law: Closed System poster for?
First Law: Closed System belongs to the Mechanical Engineering section rather than to a school year, because engineering is not something one grade owns. Anyone learning thermofluids can pin it up — a beginner, a student mid-course, or someone revising years later.
When should you use the First Law: Closed System poster?
Pistons, sealed vessels, and any fixed mass with nothing flowing across it. A wall chart earns its place by being glanceable from where the work is happening, so First Law: Closed System belongs on the wall where that engineering work actually happens, within glancing distance, rather than filed away.
What other posters go with First Law: Closed System?
Bernoulli's Equation, Continuity and Drag & Lift sit alongside First Law: Closed System in the Mechanical Engineering section. Printed together they make a wall rather than a single sheet, which is how a reference set actually gets used.Bernoulli's EquationContinuityDrag & Lift
Is the First Law: Closed System poster free to download and print?
Yes. First Law: Closed System downloads as a free PDF with no account, no email and no watermark, like everything else in the Mechanical Engineering section. Print as many copies as you like for a home, a classroom, a library or a tutoring group; reselling the file is the only thing the licence rules out.Read the licence
What size does the First Law: Closed System poster print at?
First Law: Closed System is a vector PDF laid out for US Letter, and prints on A4 with Fit to page — the same file, no separate download. Because every mark on it is drawn rather than photographed, it stays sharp enlarged to A3, A2 or A1 at a copy shop. Colour carries emphasis only, so a greyscale print of First Law: Closed System loses nothing.Printing guide

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