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 254 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 325 K when this process starts, and the temperature in the cold compartment of the refrigerator be 264 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=1-254/325=0.21846
hence heat gain by the room/time=254*0.21846=55.48884
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)=254 W
hence there should be an increase in the internal energy of the room.

work done +heat=internal energy

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.