Who left the fridge open?
Classical Mechanics
Level
1
You accidentally leave the refrigerator door in your home open. After the refrigerator runs for an hour with the door open, is the average temperature in your home higher or lower than it was before?
Assume that...
- negligible thermal energy passes in or out of the outer boundary of your home (i.e. your home is perfectly insulated)
- the "average temperature in your home" is the average temperature of any and all matter within the outer boundary of your home
- the refrigerator uses electricity to lower the temperature of the air inside the refrigerator below that of the surrounding air by some unspecified means.
- the air in the refrigerator starts out at a lower temperature than the rest of your home
Exactly the same
There isn't enough information to tell
Higher
Lower
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1 solution
Carnot's theorem tells us that it's impossible for a heat pump to move thermal energy from a cold reservoir (the fridge) to a hot reservoir (the air around the fridge) without doing nonzero work. Therefore, the thermal energy exhausted into the hot reservoir is greater than that taken from the cold reservoir (the difference in energy coming from the electrical energy used by the pump).
Therefore, the total thermal energy of your perfectly-insulated home is increasing, and so must the average temperature.