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JEE Main 2020 (2 Sep, Shift 2) · Heat Engines, Refrigerators & Second Law

Heat Engines, Refrigerators & Second Law question from JEE Main 2020 (2 Sep, Shift 2)

Q52JEE Main 2020 · 2 SEP · SHIFT 2Medium

Heat Engines, Refrigerators & Second Law

A heat engine is involved with exchange of heat of 1915 J, – 40J, + 125 J and –Q J, during one cycle achieving an efficiency of 50.0%. The value of Q is

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Answer: (a)

  1. Heat absorbed Qin=1915+125=2040 JQ_{in} = 1915 + 125 = 2040\text{ J}.
  2. Net work W=1915−40+125−Q=2000−QW = 1915 - 40 + 125 - Q = 2000 - Q.
  3. η=WQin\eta = \frac{W}{Q_{in}}: 0.5×2040=2000−Q⇒Q=980 J0.5 \times 2040 = 2000 - Q \Rightarrow Q = 980\text{ J}
  4. So the answer is (a) 980 J.
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