Q147 / 160 · AP EAMCET 2020 (21 Sep Shift 2) · Physics

The efficiency of a Carnot's engine is \(100 \%\) only when

  • A
    ideal gas is used as a working substance
  • Correct answer
    B
    temperature of the sink is equal to absolute zero
  • C
    source temperature is equal to the temperature of the sink
  • D
    source temperature is equal to absolute zero

Solution

The efficiency of Carnot's engine is given as \(\eta=1-\frac{T_2}{T_1}\) ...(i) where, \(T_1=\) temperature of source and \(T_2=\) temperature of sink. For \(100 \%\) efficiency, \(\eta=1\) \(\therefore\) From Eq. (i), we get \(1=1-\frac{T_2}{T_1} \Rightarrow \frac{T_2}{T_1}=0 \Rightarrow T_2=0\) Hence, temperature of \(\operatorname{sink} T_2\) is equal to absolute zero.

Hence, the correct answer is option: 'B'.

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