Brain Teasers
Refrigerator
On a hot summer day, a man who had no air conditioning decided that he would cool off his home by leaving the door to his refrigerator open. Does he succeed in cooling off his home?
Hint
Do an energy balance.Answer
No. All a refrigerator does is take heat from inside the unit and pump it to the back. So doing an energy balance would lead to the conclusion that no cooling overall takes place. Further investigation would reveal that the home would actually heat up since refrigerators need an electric motor to operate. This would generate additional heat, making the home hotter.Hide Hint Show Hint Hide Answer Show Answer
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Comments
I wounder how many people have accually tried it.
me 2!!
Haha, I liked this one. I know the old man would have probably been me if I were in his shoes!
It seems to me that with the door shut, the room is at a certain temperature and the inside of the fridge is at a much cooler temperature. When he first opens the door, the temperature of the room will try to equalize by moving a bunch of heat into the fridge. This will lower the overall temperature of the room at least initially. Then the temperature will rise back up to the normal hot temperature and it will stay that way. So it would be a quick, but not a permanent solution.
In reference to Jake's comments, the fridge will overcompensate for eing open, and will work harder. The heat generated by the heat exchanger will raise the temp of the room, actually making the room hotter.
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