|
edit: Updated with my response, thanks for the discussion.
Just had this question on a test. I think it's just a poorly thought-out question and the answer is somewhat up to interpretation. What do TL'ers think? Obviously only answer if you think you know what the answer should be and feel free to give an explanation.
"When a thermometer is submerged in a liquid, the Zeroth Law of Thermodynamics tells us that the temperature of the thermometer is the same as that of the liquid"
a) True
b) False
Poll: So...False (48) 80% True (12) 20% 60 total votes Your vote: So... (Vote): True
(Vote): False
I'll hold off a bit on saying what I answered and why.
Fun fact: This is the first google image results for "thermodynamics" as I've just discovered:
+ Show Spoiler +
I said false thinking that the zeroth law wasn't applicable since there weren't 3 distinct objects/systems present and the question never mentions anything about equilibrium or if the thermometer has been submerged for a long period of time.
|
Assuming that the system is in thermal equlibrium yes.
However the question says nothing about that so the correct answer should be "not necessarily"? I dunnu.
|
its not necessarily equal, if you heat up the thermometer then put it into liquid it would take time to reach equilibrium
|
On April 19 2011 06:55 KlaCkoN wrote:
Assuming that the system is in thermal equlibrium yes.
However the question says nothing about that so the correct answer should be "not necessarily"? I dunnu.
Didn't take very long for someone to nail it.
|
I'd say yes. q= m *C *deltaT right? Also, that comic is pretty funny haha
|
Its a shame I know nothing of this subject, I hate looking at pictures and not understanding what it means. I feel like I am missing out on a joke... perhaps someone can explain the comic to me?
|
On April 19 2011 07:14 WarChimp wrote:
Its a shame I know nothing of this subject, I hate looking at pictures and not understanding what it means. I feel like I am missing out on a joke... perhaps someone can explain the comic to me?
Thermodynamics state that the universe is heading into increased (entropy) chaos.
|
United States5162 Posts
I've never heard of the Zeroth Law, so after Googling it I found it's a generalization about things in equilibrium. As such, I think if something is following the Zeroth Law that you would assume it's in equilibrium or else the Zeroth law wouldn't apply at all.
EDIT; However, in this case I think the answer would be false because the Zeroth law deals with 3 objects, not two.
|
Calgary26003 Posts
I don't get why everyone voted yes. In my eyes, this situation isn't even related to the zeroth law of thermodynamics.
So no.
|
Calgary26003 Posts
On April 19 2011 07:18 Myles wrote:
I've never heard of the Zeroth Law, so after Googling it I found it's a generalization about things in equilibrium. As such, I think if something is following the Zeroth Law that you would assume it's in equilibrium or else the Zeroth law wouldn't apply at all.
It also talks about three bodies. As such, should we just assume there's some other relevent third body too? O_o
|
On April 19 2011 07:19 Chill wrote:Show nested quote +On April 19 2011 07:18 Myles wrote:
I've never heard of the Zeroth Law, so after Googling it I found it's a generalization about things in equilibrium. As such, I think if something is following the Zeroth Law that you would assume it's in equilibrium or else the Zeroth law wouldn't apply at all. It also talks about three bodies. As such, should we just assume there's some other relevent third body too? O_o
Yeah. Was reading it on wikipedia, and where the hell is the third body o.o
|
United States5162 Posts
On April 19 2011 07:19 Chill wrote:Show nested quote +On April 19 2011 07:18 Myles wrote:
I've never heard of the Zeroth Law, so after Googling it I found it's a generalization about things in equilibrium. As such, I think if something is following the Zeroth Law that you would assume it's in equilibrium or else the Zeroth law wouldn't apply at all. It also talks about three bodies. As such, should we just assume there's some other relevent third body too? O_o
Yup(well, no to your question...but you get it), after stepping back for a second it became clear this is just a cleverly disguised question on whether you know what the Zeroth law is, not whether anything is actually in equilibrium.
|
On April 19 2011 07:21 Froadac wrote:Show nested quote +On April 19 2011 07:19 Chill wrote:On April 19 2011 07:18 Myles wrote:
I've never heard of the Zeroth Law, so after Googling it I found it's a generalization about things in equilibrium. As such, I think if something is following the Zeroth Law that you would assume it's in equilibrium or else the Zeroth law wouldn't apply at all. It also talks about three bodies. As such, should we just assume there's some other relevent third body too? O_o Yeah. Was reading it on wikipedia, and where the hell is the third body o.o
If there's no 3rd body, then doesn't that mean the Zeroth Law isn't telling us anything in this situation so the answer is just false?
|
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different.
|
United States5162 Posts
On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different.
It's actually not. The question isn't about the temperature or equilibrium at all. It's about what the Zeroth Law tells us, which in this case is nothing because the Zeroth law applies to 3 bodies, not 2.
|
Calgary26003 Posts
On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different.
But even if it's the same, the zeroth law doesn't tell us that.
|
It's a combination of the first and second laws of thermodynamics that tells you an object placed in contact with a thermal reservoir (allowing heat to pass between them) will result in the thermometer measuring the temperature of the liquid (eventually).
Assuming the thermometer is intended to be the object and the liquid is well approximated as a thermal reservoir, and that the thermometer actually works (sort of by definition it must, or it's not a thermometer), anyway.
You do need the zeroth law I think, to define what is meant by thermal equilibrium though. So in that sense it's true.
Also I've written the word thermometer so many times it no longer looks like a real word any more.
|
On April 19 2011 07:25 dudeman001 wrote:Show nested quote +On April 19 2011 07:21 Froadac wrote:On April 19 2011 07:19 Chill wrote:On April 19 2011 07:18 Myles wrote:
I've never heard of the Zeroth Law, so after Googling it I found it's a generalization about things in equilibrium. As such, I think if something is following the Zeroth Law that you would assume it's in equilibrium or else the Zeroth law wouldn't apply at all. It also talks about three bodies. As such, should we just assume there's some other relevent third body too? O_o Yeah. Was reading it on wikipedia, and where the hell is the third body o.o If there's no 3rd body, then doesn't that mean the Zeroth Law isn't telling us anything in this situation so the answer is just false?
Ugg yeah, re-reading the question and remembering what the zeroth law actually says I think that's right.
Stupid question imo :p
|
Just a badly written question is all. Happens all the time on tests unfortunately. If really pushed I'd go with "no" because the zeroth law doesn't seem to have much to do with this situation, but I wouldn't feel good about it.
|
On April 19 2011 07:36 Myles wrote:Show nested quote +On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different. It's actually not. The question isn't about the temperature or equilibrium at all. It's about what the Zeroth Law tells us, which in this case is nothing because the Zeroth law applies to 3 bodies, not 2.
Lol, you are completely missing the point of the Zeroth Law of thermodynamics.........
The point is that the liquid, glass, mercury, and air are all in equilibrium with each other. Without the zeroth law even if the liquid and glass were in equilibrium and the glass and mercury were in equilibrium. The liquid and mercury would not be in equilibrium. Without this it would be impossible to measure temperature.
Look, just because in grade school math A=B, B=C ==> A=C does not mean it is always the case.
|
On April 19 2011 07:38 Chill wrote:Show nested quote +On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different. But even if it's the same, the zeroth law doesn't tell us that.
But then there is not enough information to answer the question. Lack of information =/= false.
|
The 'three bodies' thing is a bit of a red herring, yes. The point is that thermal equilibrium doesn't really mean much without the zeroth law, as there's no way you can use "A is in equilibrium with B" to infer anything else about B or A (even as trivial as "B is in equilibrium with A" doesn't neccessarily follow).
|
United States5162 Posts
On April 19 2011 07:46 SirazTV wrote:Show nested quote +On April 19 2011 07:36 Myles wrote:On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different. It's actually not. The question isn't about the temperature or equilibrium at all. It's about what the Zeroth Law tells us, which in this case is nothing because the Zeroth law applies to 3 bodies, not 2. Lol, you are completely missing the point of the Zeroth Law of thermodynamics......... The point is that the liquid, glass, mercury, and air are all in equilibrium with each other. Without the zeroth law even if the liquid and glass were in equilibrium and the glass and mercury were in equilibrium. The liquid and mercury would not be in equilibrium. Without this it would be impossible to measure temperature. Look, just because in grade school math A=B, B=C ==> A=C does not mean it is always the case.
Huh? I think you're reading a bit too much into the question. It's says nothing about anything being in equilibrium. It talks about two bodies, the thermometer and the liquid. Talking about the components of the thermometer, or the air or the glass is adding extra info that isn't given. As pointed out by others, we have no idea at what temperature anything is at or how long the things have been in contact.
The whole question is does Zeroth law tell you that the two objects are in equilibrium, which is no.
|
On April 19 2011 07:48 SirazTV wrote:Show nested quote +On April 19 2011 07:38 Chill wrote:On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different. But even if it's the same, the zeroth law doesn't tell us that. But then there is not enough information to answer the question. Lack of information =/= false.
Nope.
You are not answering true/false as to whether or not the temperature is the same, but to whether or not the zeroth law says it is. Since there's no third system, it doesn't, so the answer is false.
|
does the 0th law of thermodynamics tell you that the temperatures are the same? No, the 0th law of thermodynamics is a principle about thermal equilibrium between three bodies. false.
this question is not poorly written nor is it open to interpretation.
|
The zeroth law applies to two systems (you let system 2 and system 3 be the same system), so you can't use that argument.
|
Calgary26003 Posts
On April 19 2011 07:48 SirazTV wrote:Show nested quote +On April 19 2011 07:38 Chill wrote:On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different. But even if it's the same, the zeroth law doesn't tell us that. But then there is not enough information to answer the question. Lack of information =/= false.
Read the question and then read the answers. Lack of information does equal false in this case.
I don't know how people are confusing this question. It doesn't even state the thermometer is at equilibrium with the liquid, just that it's submerged. The liquid could be ice water and the thermometer could be a hundred degrees. That's not at equilibrium so the zeroth law doesn't tell us anything in this situation.
|
Well part of interpreting exam questions is understanding the context, and half of a physics exam is making the appropriate assumptions. It's hardly a surprise people are making sensible assumptions given the question (e.g. that 'submerged' means it's been there long enough to thermalise with the surroundings), but since it's either badly worded or a trick question, it's not entirely clear what those assumptions should be.
|
On April 19 2011 07:48 SirazTV wrote:Show nested quote +On April 19 2011 07:38 Chill wrote:On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different. But even if it's the same, the zeroth law doesn't tell us that. But then there is not enough information to answer the question. Lack of information =/= false.
Usually a true/false question is understood as asking whether a proposition is a tautology, i.e. whether it is true for every allowed value of the variables involved.
|
When such a question strikes you ask the teacher holding the exam what he/she is asking with the question. Not being able to understand a poorly formulated/constructed question shouldn't lose you points.
Since we can't do that (answering afterwards) I would have to go with false due to the reasons others have stated. Not enough information equals false.
Another option would be to expand upon the question options, tick false and then give a reason so you show you understood the material but that the question tricked you if you answer incorrectly. (This doesn't work if it is scanned and just checks the area for the answer and automagically corrects it afterwards.)
|
Thanks for the responses so far. Yurie, that's a good idea.
|
Eventually yes, they'll be the same temperature (thermo equilibrium) so true
Edit: Clarification: An important corollary of the zeroth law is as follows "Two systems are in thermal equilibrium if and only if they have the same temperature"
Second Edit: I went back and checked my text just to make sure, they mention this exact example (I assume its the standard example), the only reason a thermometer is useful is because it measures its own temperature which, by zeroth law, is the temperature of its surrounding. Ignore the formal 3 bodies definition, that's not whats important.
Third Edit: Granted the question is ambiguous as whether or not the thermometer is in equilibrium with the water but, because it doesn't say one way or another, we can logically assume that it is since we're talking about a thermometer. Its only use is when its in equilibrium and it reaches that relatively quickly, I think the other posters in this thread are over thinking it
|
Ah, but DieJokes, the thermometer only has the temperature of the surroundings thanks to the first and second laws. 
I don't think it's a very good question but you are probably right, that is what the teacher is trying to get at with the question.
|
Chill nailed it. The question isn't whether the thermometer and liquid are the same temperature, it's whether the Zeroth Law tells you that they are, which it clearly doesn't.
|
On April 19 2011 06:55 KlaCkoN wrote:
Assuming that the system is in thermal equlibrium yes.
However the question says nothing about that so the correct answer should be "not necessarily"? I dunnu.
Yeah this is what I figure as well.
|
I get dumb questions like these in physics all the time, they try to fake that they are ambiguous. But if you sit down and think about it, you really just have to look at the wording of the question. The wording asks about the Zeroth law, meaning you are verifying whether or not the situation follows the zeroth law (regardless of what the result of the situation is).
I always hated them.
|
On April 19 2011 09:04 Dragar wrote:Ah, but DieJokes, the thermometer only has the temperature of the surroundings thanks to the first and second laws. I don't think it's a very good question but you are probably right, that is what the teacher is trying to get at with the question.
Well, not directly right? As I understand it (I'm a first year chem major) the zeroth law came after the other three so it was discovered using the intuitive concepts that followed from the but it is fundamental to all three of them (hence zeroth). So sure you could come up with that from the first two, but the first two don't actually say that.
On April 19 2011 09:27 Vertig0 wrote:
Chill nailed it. The question isn't whether the thermometer and liquid are the same temperature, it's whether the Zeroth Law tells you that they are, which it clearly doesn't.
The zeroth law does tell you this, but not directly from the formal definition. If you look in your texts they'll describe exactly this situation as an application of the zeroth law, a cursory glance at the wiki isn't sufficient (not to say you did that, but I think some other people in the thread have; please don't take any of this personally I don't mean it to be)
|
On April 19 2011 10:04 n.DieJokes wrote:Show nested quote +On April 19 2011 09:04 Dragar wrote:Ah, but DieJokes, the thermometer only has the temperature of the surroundings thanks to the first and second laws. I don't think it's a very good question but you are probably right, that is what the teacher is trying to get at with the question. Well, not directly right? As I understand it (I'm a first year chem major) the zeroth law came after the other three so it was discovered using the intuitive concepts that followed from the but it is fundamental to all three of them (hence zeroth). So sure you could come up with that from the first two, but the first two don't actually say that.
Sort of directly. Thermometers work (in the sense that they reach the same temperature as their surroundings) because of the first and second laws.
(I think the simplest way to put is is that the first law tells us how heat and entropy are related, and the second law tells us how entropy behaves - the combination allowing us to deduce how heat will flow between the thermometer and its surroundings when out of equilibrium.)
The zeroth law is indeed fundamental, as it gives you a meaning behind temperature (equilibrium) in the first place.
|
On April 19 2011 10:10 Dragar wrote:Show nested quote +On April 19 2011 10:04 n.DieJokes wrote:On April 19 2011 09:04 Dragar wrote:Ah, but DieJokes, the thermometer only has the temperature of the surroundings thanks to the first and second laws. I don't think it's a very good question but you are probably right, that is what the teacher is trying to get at with the question. Well, not directly right? As I understand it (I'm a first year chem major) the zeroth law came after the other three so it was discovered using the intuitive concepts that followed from the but it is fundamental to all three of them (hence zeroth). So sure you could come up with that from the first two, but the first two don't actually say that. Sort of directly. Thermometers work (i.e. they reach the same temperature as their surroundings) because of the first and second laws. The zeroth law is indeed fundamental, as it gives you a meaning behind temperature in the first place.
I get what you're saying, but the zeroth tells us that they will have exactly the same temperature at equilibrium; you can't get that directly from the first or more importantly the second law.
Edit: That seems ambiguous; the second law says energy is conserved in the system and acts in such a way as to decrease potential energy. So from this the thermometer will heat or cool depending on its surrounds and vice versa. It's the zeroth law that tells us that this system reaches equilibrium if and only if they have exactly the same temperature. It doesn't matter what the materials are, they will reach the same temp.
|
On April 19 2011 07:46 SirazTV wrote:Show nested quote +On April 19 2011 07:36 Myles wrote:On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different. It's actually not. The question isn't about the temperature or equilibrium at all. It's about what the Zeroth Law tells us, which in this case is nothing because the Zeroth law applies to 3 bodies, not 2. Lol, you are completely missing the point of the Zeroth Law of thermodynamics......... The point is that the liquid, glass, mercury, and air are all in equilibrium with each other. Without the zeroth law even if the liquid and glass were in equilibrium and the glass and mercury were in equilibrium. The liquid and mercury would not be in equilibrium. Without this it would be impossible to measure temperature. Look, just because in grade school math A=B, B=C ==> A=C does not mean it is always the case.
I can think of no system where using the operator =, A, B and C the way that you have and with the parameters that you have, that a person would be unable to infer a relationship between A and C. Perhaps choose your operators better next time you decide to be a smarmy ass.
|
On April 19 2011 08:26 Chill wrote:Show nested quote +On April 19 2011 07:48 SirazTV wrote:On April 19 2011 07:38 Chill wrote:On April 19 2011 07:34 SirazTV wrote:
That is an example of a question that is a terrible true or false question. Both answers are wrong as the temperature could be the same or different. But even if it's the same, the zeroth law doesn't tell us that. But then there is not enough information to answer the question. Lack of information =/= false. Read the question and then read the answers. Lack of information does equal false in this case. I don't know how people are confusing this question. It doesn't even state the thermometer is at equilibrium with the liquid, just that it's submerged. The liquid could be ice water and the thermometer could be a hundred degrees. That's not at equilibrium so the zeroth law doesn't tell us anything in this situation.
Basically this. You are not given enough information for the zeroth law to apply, so the answer is false. Pretty easy question as long as you don't overthink it.
|
On April 19 2011 10:21 n.DieJokes wrote:Show nested quote +On April 19 2011 10:10 Dragar wrote:On April 19 2011 10:04 n.DieJokes wrote:On April 19 2011 09:04 Dragar wrote:Ah, but DieJokes, the thermometer only has the temperature of the surroundings thanks to the first and second laws. I don't think it's a very good question but you are probably right, that is what the teacher is trying to get at with the question. Well, not directly right? As I understand it (I'm a first year chem major) the zeroth law came after the other three so it was discovered using the intuitive concepts that followed from the but it is fundamental to all three of them (hence zeroth). So sure you could come up with that from the first two, but the first two don't actually say that. Sort of directly. Thermometers work (i.e. they reach the same temperature as their surroundings) because of the first and second laws. The zeroth law is indeed fundamental, as it gives you a meaning behind temperature in the first place. I get what you're saying, but the zeroth tells us that they will have exactly the same temperature at equilibrium; you can't get that directly from the first or more importantly the second law.
Yes, I don't disagree. But you will have no reason to believe a thermometer is ever in equilibrium with its surroundings without the other laws.
Edit: I saw your edit. Yes, precisely (although we do still need the first law to relate energy to heat!).
|
On April 19 2011 10:26 Dragar wrote:Show nested quote +On April 19 2011 10:21 n.DieJokes wrote:On April 19 2011 10:10 Dragar wrote:On April 19 2011 10:04 n.DieJokes wrote:On April 19 2011 09:04 Dragar wrote:Ah, but DieJokes, the thermometer only has the temperature of the surroundings thanks to the first and second laws. I don't think it's a very good question but you are probably right, that is what the teacher is trying to get at with the question. Well, not directly right? As I understand it (I'm a first year chem major) the zeroth law came after the other three so it was discovered using the intuitive concepts that followed from the but it is fundamental to all three of them (hence zeroth). So sure you could come up with that from the first two, but the first two don't actually say that. Sort of directly. Thermometers work (i.e. they reach the same temperature as their surroundings) because of the first and second laws. The zeroth law is indeed fundamental, as it gives you a meaning behind temperature in the first place. I get what you're saying, but the zeroth tells us that they will have exactly the same temperature at equilibrium; you can't get that directly from the first or more importantly the second law. Yes, I don't disagree. But you will have no reason to believe a thermometer is ever in equilibrium with its surroundings without the other laws.
Ah, I get it. lol, I don't have any good response to that, seems like a valid issue... I just assumed the other laws were in effect. It feels to nit picky to me, idk
|
the answer is no
the question says WHEN the blah blah blah
but heat takes time to flow from 1 thing to another so at the moment its submerged they wont have the exact same temperature
|
On April 19 2011 10:36 n.DieJokes wrote:Show nested quote +On April 19 2011 10:26 Dragar wrote:On April 19 2011 10:21 n.DieJokes wrote:On April 19 2011 10:10 Dragar wrote:On April 19 2011 10:04 n.DieJokes wrote:On April 19 2011 09:04 Dragar wrote:Ah, but DieJokes, the thermometer only has the temperature of the surroundings thanks to the first and second laws. I don't think it's a very good question but you are probably right, that is what the teacher is trying to get at with the question. Well, not directly right? As I understand it (I'm a first year chem major) the zeroth law came after the other three so it was discovered using the intuitive concepts that followed from the but it is fundamental to all three of them (hence zeroth). So sure you could come up with that from the first two, but the first two don't actually say that. Sort of directly. Thermometers work (i.e. they reach the same temperature as their surroundings) because of the first and second laws. The zeroth law is indeed fundamental, as it gives you a meaning behind temperature in the first place. I get what you're saying, but the zeroth tells us that they will have exactly the same temperature at equilibrium; you can't get that directly from the first or more importantly the second law. Yes, I don't disagree. But you will have no reason to believe a thermometer is ever in equilibrium with its surroundings without the other laws. Ah, I get it. lol, I don't have any good response to that, seems like a valid issue... I just assumed the other laws were in effect. It feels to nit picky to me, idk
It is nit picky, but so is physics. 
It's a badly worded question.
|
Oh btw updated the OP with how I answered (I said false). Taking the exam almost made me angry because I had a feeling false was the better answer, but that she wanted true.... so dumb. Got it back today and the "correct" answer was true. Going to "ask" her about it on Wednesday during office hours and get owned since she's the prof.
I can see it now...
".... no you don't understand, people on the sc website TOLD ME SO!!!"
edit: btw Chill broke the poll once he posted, it was like 6 true, 1 false at one point.
|
On April 19 2011 14:44 Jonoman92 wrote:
Oh btw updated the OP with how I answered (I said false). Taking the exam almost made me angry because I had a feeling false was the better answer, but that she wanted true.... so dumb. Got it back today and the "correct" answer was true. Going to "ask" her about it on Wednesday during office hours and get owned since she's the prof.
I can see it now...
".... no you don't understand, people on the sc website TOLD ME SO!!!"
edit: btw Chill broke the poll once he posted, it was like 6 true, 1 false at one point.
I still think true is the answer that's most in the spirit of the question. Every argument I've heard otherwise is really ballbustingly technical for a true false but gl!
|
Calgary26003 Posts
On April 19 2011 14:44 Jonoman92 wrote:
Oh btw updated the OP with how I answered (I said false). Taking the exam almost made me angry because I had a feeling false was the better answer, but that she wanted true.... so dumb. Got it back today and the "correct" answer was true. Going to "ask" her about it on Wednesday during office hours and get owned since she's the prof.
I can see it now...
".... no you don't understand, people on the sc website TOLD ME SO!!!"
edit: btw Chill broke the poll once he posted, it was like 6 true, 1 false at one point.
I can't accept this answer. The word that rubs me the wrong way is "submerged".
Obviously the intent is that when something is submerged in a liquid for long enough, they are at thermal equilibrium. This question makes no statement on time.
Clearly you can see me holding an icecube submerged in a hot glass of coffee and one second later asking this question. Are they the same temperature? Fuck no. Will they be in a minute? Yes of course.
Things don't necessarily need to be the same temperature to be in thermal equilibrium; however, Qin must equal Qout. There is zero energy generation from a thermometer. If the thermometer is hotter than the liquid, there is going to be heat dissipation through conduction, at the minimum. This system isn't in thermal equilibrium.
Yes, it could be in thermal equilibrium, but the question never states that. If we're going to start making assumptions like that, well then you'd better just quit this class because you can just start assuming every system has an efficiency of 0% and thus transfers zero mass and finish your final in 2 seconds.
|
On April 20 2011 00:06 Chill wrote:Show nested quote +On April 19 2011 14:44 Jonoman92 wrote:
Oh btw updated the OP with how I answered (I said false). Taking the exam almost made me angry because I had a feeling false was the better answer, but that she wanted true.... so dumb. Got it back today and the "correct" answer was true. Going to "ask" her about it on Wednesday during office hours and get owned since she's the prof.
I can see it now...
".... no you don't understand, people on the sc website TOLD ME SO!!!"
edit: btw Chill broke the poll once he posted, it was like 6 true, 1 false at one point. I can't accept this answer. The word that rubs me the wrong way is "submerged". Obviously the intent is that when something is submerged in a liquid for long enough, they are at thermal equilibrium. This question makes no statement on time. Clearly you can see me holding an icecube submerged in a hot glass of coffee and one second later asking this question. Are they the same temperature? Fuck no. Will they be in a minute? Yes of course. Things don't necessarily need to be the same temperature to be in thermal equilibrium; however, Qin must equal Qout. There is zero energy generation from a thermometer. If the thermometer is hotter than the liquid, there is going to be heat dissipation through conduction, at the minimum. This system isn't in thermal equilibrium. Yes, it could be in thermal equilibrium, but the question never states that. If we're going to start making assumptions like that, well then you'd better just quit this class because you can just start assuming every system has an efficiency of 0% and thus transfers zero mass and finish your final in 2 seconds.
Had a kid in one of my classes try to be a smartass and write assumptions all over his final. He got to retake it because the professor felt bad giving the kid a fail due to one moment of stupidity.
|
|
|
|
|
|
EPT![[image loading]](http://i54.tinypic.com/2gv1ona.gif)
