A heat engine operates between a cold reservoir at temperature T2 = 400 K and a hot reservoir at temperature T1. It takes 300 J of heat from the hot reservoir and delivers 240 J of heat to the cold reservoir in a cycle. The minimum temperature of the hot reservoir has to be ______________ K.
Answer (integer)
500
Solution
Q<sub>in</sub> = 300 J ; Q<sub>out</sub> = 240 J<br><br>Work done = Q<sub>in</sub> $-$ Q<sub>out</sub> = 300 $-$ 240 = 60 J<br><br>Efficiency = ${W \over {{Q_{in}}}} = {{60} \over {300}} = {1 \over 5}$<br><br>efficiency = $1 - {{{T_2}} \over {{T_1}}}$<br><br>$${1 \over 5} = 1 - {{400} \over {{T_1}}} \Rightarrow {{400} \over {{T_1}}} = {4 \over 5}$$<br><br>T<sub>1</sub> = 500 k
About this question
Subject: Physics · Chapter: Thermodynamics · Topic: Zeroth and First Law
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