Tagged Questions
2
votes
2answers
57 views
What is the derivation for the exponential energy relation and where does it apply?
Very often when people state a relaxation time $\tau_\text{kin-kin}, \tau_\text{rot-kin}$,, etc. they think of a context where the energy relaxation goes as $\propto\text e^{-t/\tau}$. Related is an ...
1
vote
3answers
132 views
Integrating factor $1/T$ in 2nd Law of Thermodynamics
How would you prove that $1/T$ is the most suitable integrating factor to transform $\delta Q$ to an exact differential in the second law of thermodynamics:
$$dS = \frac{\delta Q}{T}$$
Where $dS$ is ...
1
vote
1answer
89 views
What are the optimal conditions to fuel your car?
I was filling my car earlier today, and noticed a sticker posted on the pump.
This pump dispenses fuel at a volumetric amount measured in standard gallons (231 cubic inches). It does not adjust ...
1
vote
2answers
145 views
Activation energy and entropy
First assertion
If a system is already in a high temperature, adding energy, will increment the entropy in a low amount (compared with a system in a lower temperature).
Question (if assertion is ...
3
votes
3answers
760 views
How can I determine density of a gas only given temperature?
I have a homework problem where exhaust is traveling through an exhaust system (assumed to be air for simplicity) from and engine and then released into the atmosphere. The exhaust is at a temperature ...
2
votes
3answers
136 views
Heat Equation Equalities
While studying the heat equation, I ran into a few equalities that I cannot understand.
For example, Fourier's law of heat conduction claims that
$$\varphi(x,t)=-K_0\frac{\partial u}{\partial x},$$
...
1
vote
1answer
467 views
How are the CPU power and temperature caculated/estimated?
From Wikipedia
The power consumed by a CPU, is approximately proportional to CPU
frequency, and to the square of the CPU voltage: $$
P = C V^2 f $$ (where C is capacitance, f is ...
2
votes
1answer
271 views
How do I find average temperature given a temperature distribution?
I was told to find the temperature distribution of a wire with a current going through it. So I found $$T(x)=T_{\infty}-\frac{\dot{q}}{km^{2}}[\frac{cosh(mx)}{cosh(mL)}-1]$$
I need to find the ...
2
votes
3answers
82 views
Certain material heating water in a recipient
I don't know how to resolve a problem, but I don't want the answer since I'm almost going to have it resolved.
What the problem says is we have 85 liters of water at 7ºC in an iron pot of 29kg. We ...
2
votes
2answers
168 views
why egg cooks slowly in mountains?
A quick Google tells me "Because water boils at a lower temperature at high altitudes". But I am not being able to understand this answer and fill-in the gap. Like, how does an egg cook in the first ...
7
votes
5answers
860 views
How do we perceive hotness or coldness of an object?
Some objects, especially metallic ones, feel cold on touching and others like wood, etc. feel warm on touching. Both are exposed to same environment and are in their stable state, so some kind of ...
1
vote
1answer
498 views
How does liquid convert to gas on getting thermal heat energy?
Say for example, when we heat, water converts to steam gas. How does it happen? What happens underneath giving rise to breaking of bond between molecules in liquid state and spreading them in gas ...
5
votes
3answers
444 views
Can temperature be defined as propensity to transmit thermal energy?
I was recently surprised to learn that defining temperature isn't easy. For a long time, it was defined operationally: how much does a thermometer expand. Also surprising, temperature isn't a ...
2
votes
2answers
746 views
In summer are the upper storey flats more hot or the lower storey flats?
I have often heard neighbours talking things like in a multi storied apartment, the upper flats are more hot in summer then lower flats (or vice versa?) and similarly for some comparison in winter? ...
1
vote
2answers
245 views
How does my air-cooling unit work?
During the winter, my office gets a little cold. I have a unit (essentially a space heater) that heats the area around it to help keep me warm.
Now that it's summer, I realize the unit also has a ...
