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A : Coefficient of performanceof a refre...

A : Coefficient of performanceof a refreigerator is always greater than 1.
R : Efficiencyof heat engine is greater than 1.

A

If both Assertion & Reason are true and the reason is the correct explantion of the assertion, then mark(1)

B

If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).

C

If Assertion is true statement but Reason is false, then mark (3).

D

If both Assertion and Reason are false statements, then mark (4)

Text Solution

AI Generated Solution

The correct Answer is:
To solve the assertion-reason question, we will analyze both the assertion (A) and the reason (R) separately. ### Step 1: Analyze the Assertion (A) The assertion states: "The coefficient of performance (COP) of a refrigerator is always greater than 1." 1. **Understanding COP**: The Coefficient of Performance (COP) for a refrigerator is defined as: \[ \text{COP} = \frac{Q_L}{W} \] where \( Q_L \) is the heat removed from the cold reservoir and \( W \) is the work input. 2. **Relation to Temperatures**: The COP can also be expressed in terms of the temperatures of the hot and cold reservoirs: \[ \text{COP} = \frac{T_L}{T_H - T_L} \] where \( T_L \) is the temperature of the cold reservoir and \( T_H \) is the temperature of the hot reservoir. 3. **Condition for COP > 1**: For the COP to be greater than 1: \[ T_L > T_H - T_L \] Rearranging gives: \[ 2T_L > T_H \quad \Rightarrow \quad T_L > \frac{T_H}{2} \] This condition does not always hold true; thus, the assertion is not universally valid. ### Conclusion for Assertion: The assertion is **false** because the COP of a refrigerator is not always greater than 1. --- ### Step 2: Analyze the Reason (R) The reason states: "The efficiency of a heat engine is greater than 1." 1. **Understanding Efficiency**: The efficiency (\( \eta \)) of a heat engine is defined as: \[ \eta = \frac{W}{Q_H} \] where \( W \) is the work output and \( Q_H \) is the heat absorbed from the hot reservoir. 2. **Relation to Temperatures**: The efficiency can also be expressed in terms of the temperatures of the hot and cold reservoirs: \[ \eta = 1 - \frac{T_L}{T_H} \] where \( T_L \) is the temperature of the cold reservoir and \( T_H \) is the temperature of the hot reservoir. 3. **Condition for Efficiency**: Since \( T_L < T_H \), it follows that: \[ \frac{T_L}{T_H} < 1 \quad \Rightarrow \quad 1 - \frac{T_L}{T_H} < 1 \] Therefore, the efficiency of a heat engine is always less than 1. ### Conclusion for Reason: The reason is **false** because the efficiency of a heat engine is never greater than 1. --- ### Final Conclusion: Both the assertion (A) and the reason (R) are false. Therefore, the correct answer is option D: "Both A and R are false." ---
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