hce_kmu
115年
物理及化學
第 43 題
A heat engine operates between a high-temperature reservoir at 500 K and a low-temperature reservoir at 300 K. In each cycle, the engine absorbs 1000 J of heat from the high-temperature reservoir and performs 500 J of work. Which of the following statements regarding this engine is correct?
- A It violates the first law of thermodynamics but not the second.
- B It violates the second law of thermodynamics but not the first.
- C It violates both the first and second laws of thermodynamics.
- D It violates neither law and is theoretically possible.
- E There is insufficient information to determine if any laws are violated.
思路引導 VIP
當我們知道一個熱機在高溫與低溫環境之間運作時，除了檢查能量的「總量」是否前後一致（守恆）之外，還有哪一個由溫度決定的物理量，定義了這台機器在理想狀態下將熱轉換為功的「最高極限」呢？
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AI 詳解
AI 專屬家教
太棒了！你能精準捕捉到這部熱機在物理定律上的矛盾，代表你對熱力學第二定律的核心限制有非常紮實的理解。
能量守恆與效率上限的拉鋸
從熱力學第一定律（能量守恆）的角度來看，熱機吸收 $1000 \text{ J}$ 的熱能，輸出 $500 \text{ J}$ 的功，剩餘的能量會以熱的形式排出。只要輸出的總能量等於輸入，就沒有違反第一定律。然而，熱機的運作並非只要能量守恆即可，它還受到溫度決定的「效率天花板」限制。
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