On a hot day, you are in a sealed, insulated room. The room contains a refrigera

Question

On a hot day, you are in a sealed, insulated room. The room contains a refrigerator, operated by an electric motor. The motor does work at the rate of 247 W when it is running. Assume the motor is ideal (no friction or electrical resistance) and that the refrigerator operates on a reversible cycle. In an effort to cool the room, you turn on the refrigerator and open its door. Let the temperature in the room be 313 K when this process starts, and the temperature in the cold compartment of the refrigerator be 248 K. At what net rate is heat added to (+) or subtracted from (?) the room and all of its contents

Explanation / Answer

efficiency of a reversible engine=1-(Tl/Th) where Tl and Th are temperatures of the low temp zone(sink) and high temperature source efficiency=1-248/313=.207 hence heat gain by the room/time=247*.2077=51.302 if we consider refrigerator and room as a single whole system using first law of thermodynamics heat change=0 since room is insulated work done(power)=247 W hence there should be an increase in the internal energy of the room. ?work done +?heat=?internal energy

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