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Thermal Physics

Quick questions on Thermodynamic processes and pV diagrams: H2 Physics Thermal Physics

6short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is work as the area under a pV curve?
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When a gas changes volume, the work done by the gas is the area under the process on a pressure-volume (pV) diagram. For a small change at pressure pp:
What is combining with the first law?
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Each process is analysed with ΔU=Q−Wby\Delta U = Q - W_{\text{by}} (using work done by the gas):
What is a closed cycle?
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A closed cycle returns the gas to its starting state, so over one complete cycle ΔU=0\Delta U = 0. The net work done in the cycle equals the area enclosed by the loop on the pV diagram:
What is q1?
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State what the area under a process on a pressure-volume diagram represents. [1 mark]
What is q2?
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A gas expands at a constant pressure of 1.5×105 Pa1.5 \times 10^5\ \text{Pa} from 2.0×10−3 m32.0 \times 10^{-3}\ \text{m}^3 to 6.0×10−3 m36.0 \times 10^{-3}\ \text{m}^3. Find the work done by the gas. [2 marks]
What is q3?
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Explain why the net change in internal energy of a gas is zero over one complete closed cycle. [2 marks]

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