Q140 / 160 · TS EAMCET 2021 (06 Aug Shift 1) · Physics

An engine performs $2000 \mathrm{~J}$ of mechanical work and discards $4000 \mathrm{~J}$ of heat each cycle. What is the thermal efficiency of the engine?

  • A
    $45.5 \%$
  • B
    $31.4 \%$
  • C
    $25 \%$
  • Correct answer
    D
    $33.3 \%$

Solution

Work done, $W=2000 \mathrm{~J}$ Heat transferred to surrounding, $Q_2=4000 \mathrm{~J}$ Let heat supplied to the engine $=Q_1$ Since, $Q_1=Q_2+W=2000+4000=6000 \mathrm{~J}$ Thermal efficiency, $\begin{aligned} \eta & =\frac{W}{Q_1} \times 100 \% \\ & =\frac{2000}{6000} \times 100 \%=33.3 \%\end{aligned}$

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

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