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bird4 · Apr 8, 2008, 07:57 AM

A Carnot refrigerator is used in a kitchen in which the temperature is kept at 304 K. This refrigerator uses 280 J of work to remove 2350 J of heat from the food inside. What is the temperature inside the refrigerator?

retsoksirhc · Apr 8, 2008, 08:02 AM

This looks like a trick question to me (though I'm no good with the math side of physics)... it doesn't say the temperature of the food, or that the temperature of the fridge changed at all. Wouldn't the temperature of the fridge be the same? Anyone?

ebaines · Apr 9, 2008, 12:09 PM

Carnot engines (and refrigerators) are idealized representations that are assumed to be in perfect working order. The effectiveness of such a refrigerator is defined to be:

$ Eff = \frac {Energy\ Removed} {Work\ Required} = \frac {Q_C} {Work} $

Efficiency is also equal to:
$ Eff = \frac {T_h} {T_h - T_c} $

So here you have:
$ \frac {T_h} {T_h - T_c} = \frac {Q_C} {Work} $

or:
$ \frac {304K} {304K - T_c} = \frac {2350} {280} $

Now solve for $T_C$ .

Here's a helpful website for reference: Carnot Engines, Heat Pumps, and Refrigerators