AIPMT PRELIMS 2001 Physics Efficiency of Heat Engines MCQ Question

The efficiency of a heat engine is given by the formula: $\eta = 1 - \frac{T_{sink}}{T_{source}}$ where temperatures must be in Kelvin. First, we convert the given temperatures from Celsius to Kelvin: $T_{source} = 127 + 273 = 400 \, K$ and $T_{sink} = 27 + 273 = 300 \, K$. Now, substituting these values into the efficiency formula: $\eta = 1 - \frac{300}{400} = 1 - 0.75 = 0.25 \text{ or } 25\%$ This means the maximum theoretical efficiency of the engine is 25%, which is less than the claimed efficiency of 26%. Therefore, it is impossible for the engine to achieve this efficiency under the given conditions. Thus, the correct answer is A. The other options are incorrect because: B) It cannot be possible if it is already less than the theoretical limit; C) It is not probable since it exceeds the maximum efficiency; D) The data provided is sufficient to determine the impossibility of the claim.