Q149 / 155 · WBJEE 2020 · Physics

Consider an engine that absorbs 130 cal of heat from a hot reservoir and delivers 30 cal heat to a cold reservoir in each cycle. The engine also consumes 2 J energy in each cycle to overcome friction. If the engine works at 90 cycles per minute, what will be the maximum power delivered to the load? [Assume the thermal equivalent of heat is $4.2 \mathrm{~J} / \mathrm{cal}]$

  • A
    $816 \mathrm{~W}$
  • B
    $819 \mathrm{~W}$
  • Correct answer
    C
    $627 \mathrm{~W}$
  • D
    $630 \mathrm{~W}$

Solution

Hint: work done per cycle $=100 \times 4.2-2=418 \mathrm{~J}$ Total work done $=418 \times 90$ Power $=\frac{418 \times 90}{60}=627 \mathrm{~W}$

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

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