Assertion : The efficiency of a heat engine can never be unity.
Reason : Efficiency of heat engine is fundamental limitation given by first law of thermodynamics.

Options

A. If both assetion and reason are true and reaasons is the correct expanation of assetion
B. If both assetion and reason are tur but reason is not the correct explanation of assetion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states that "The efficiency of a heat engine can never be unity."

- **Understanding Efficiency**: Efficiency (η) of a heat engine is defined as the ratio of the work done (W) by the engine to the heat energy (Q_h) absorbed from the hot reservoir:
\[ \eta = \frac{W}{Q_h} \]

- **Reasoning**: In any real heat engine, not all the heat energy absorbed can be converted into work due to various losses (like friction, heat loss to the surroundings, etc.). The maximum efficiency is given by the Carnot engine, which is an ideal case. However, even for the Carnot engine, the efficiency is less than 1 because it operates between two temperature reservoirs. Therefore, the assertion is true.

### Step 2: Analyze the Reason
The reason states that "Efficiency of a heat engine is a fundamental limitation given by the first law of thermodynamics."

- **Understanding the First Law**: The first law of thermodynamics states the principle of conservation of energy, which means energy cannot be created or destroyed, only transformed from one form to another. It does not specifically limit the efficiency of heat engines.

- **Correct Principle**: The limitations on the efficiency of heat engines are actually derived from the second law of thermodynamics, which introduces the concept of entropy and the irreversibility of real processes. Thus, the reason is false.

### Conclusion
- **Assertion**: True (the efficiency of a heat engine can never be unity).
- **Reason**: False (the limitation is given by the second law of thermodynamics, not the first).

### Final Answer
The correct option is: Assertion is true, but the reason is false.

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