An aluminum conductor (resistance 50 ohms, mass 15g, specific heat capacity 0.215) in plced in liquid N2 (-195.8C). How much N2 will evaporate while the resistor cools from 20 deg C to the N2 temp?? The conductor is not connected to a power source and the container is NOT insulated. (This is an ALGEBRA based physics question).
So far I have tried: deltaQ=mass x sp. heat of aluminum x deltaT
AND deltaQ=the latent heat of vaporization of N2 (47.8) x delta mass.
Sadly (and not surprisingly for me...neither works out).
Any help would be greatly appreciated.
2006-10-09 12:53:06 · 4 answers · asked by BugGurl 3 in Science & Mathematics ➔ Physics
As the nitrogen is already at boiling point, you seem to have everything fine except the latent heat is wrong. It's 200J/g. Maybe you have it in Calories there?
2006-10-09 13:12:19 · answer #1 · answered by Anonymous · 0⤊ 0⤋
When you check your work, be sure to check your units, so you're not quietly substituting kilograms for grams. You can actually get a lot of help yourself simply by expressing this question clearly, fully, and accurately. How much is the resistor temperature changing? How much heat is the resistor losing? How much N2 will that evaporate? All in what (consistent) units? Write it all down clearly, step by step. Usually that's enough to show you where you went wrong. Another useful trick is to look at this again tomorrow.
2006-10-09 13:08:41 · answer #2 · answered by Frank N 7 · 0⤊ 0⤋
In a case like this, it is much easier to help you if you would enumerate the data with numbers attached to them.
For example, I would question what deltaTemp did you use, did you put -195.8-20=-215.8 or did you put 175.8 (wrong).
Your approach seems to be correct, so continue working on it so people can help you spot the problem, if there is any.
Although rare, but sometimes the answers are incorrect.
In physics, it is very adviseable to put a unit to all your numerical values. For example 47.8 is the latent heat of evaporation of nitrogen in calories per gram, etc.
2006-10-09 13:05:50 · answer #3 · answered by mathpath 2 · 0⤊ 0⤋
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2016-12-26 14:29:59 · answer #4 · answered by ludwig 3 · 0⤊ 0⤋