Tagged Questions
1
vote
2answers
68 views
Can a hybrid vehicle ever be more efficient than a hydrocarbon-only vehicle built with the same parts?
Based on the laws of thermodynamics, shouldn't it be theoretically impossible for a non plug-in hybrid vehicle to ever be more fuel-efficient than a vehicle that connects the same engine directly to ...
1
vote
0answers
82 views
How much money does an unused but plugged-in cellphone-charger waste in a year, if its not getting warm?
Is it right as xkcd states:
You can use heat flow to come up with simple rule of thumb: If an unused charger isn’t warm to the touch, it’s using less than a penny of electricity a day.
Or, more ...
3
votes
1answer
127 views
How can gas from compressed air can “take” heat from surrounding environment?
I have recently been reading about why a can of compressed air gets cold when the air it contains is discharged. From what I understand the change from a liquid to a gas requires energy and therefore ...
4
votes
3answers
368 views
Can I take heat from the air and convert it to electricity?
Its a summer day and the air in my house has been heated up. I could switch on my air conditioning, but then I'd be using energy from the grid in order to reduce the amount of energy in my house.
...
3
votes
3answers
252 views
Vacuum energy and perpetual motion
The part of the Einstein equations of general relativity referred to vacuum energy, introduce a repulsive term in gravity. This means that as the space become bigger and bigger, vacuum part become ...
6
votes
4answers
158 views
Is energy extensivity necessary in thermodynamics?
Given a partition of a system into two smaller systems, the energy $U$ is devided into $U_1$ and $U_2$, with
$$U=\mathcal{P}(U_1,U_2):=U_1+U_2,$$
so that $U_2$ is given by $U-U_1$. Here the ...
2
votes
1answer
149 views
Man on treadmill and energy/mass conservation
Suppose we put a very obese man inside a large air tight isolated room with a treadmill and he runs on the treadmill for 24 hours and at the end of the day he sees his weight has come down (mostly ...
1
vote
2answers
509 views
Are information conservation and energy conservation related?
as evident from the title, are both, conservation of energy and conservation of information two sides of the same coin??
Is there something more to the hypothesis of hawking's radiation other than ...
2
votes
3answers
85 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 ...
0
votes
0answers
162 views
Mixing ice and hot water [closed]
The problem in question says:
Hot water is mixed with an amount of ice having an equal mass to that of the water and an initial temperature of 0 °C. The specific heat capacity of water is 4.2 ...
3
votes
2answers
299 views
Does the global financial system violate laws of thermodynamics and energy conservation?
For the past years I am thinking about relating concepts from physics to concepts from economics. Especially since the financial crisis made obvious the instability of the financial system I ask ...
1
vote
3answers
417 views
Why isn't pressure a measure of energy?
Hey guys, I'm having a problem in understanding the 1st Law of Thermodynamics.
If i would increase the pressure of a closed system by compressing a gas in a cylinder isothermal, the 1.Law states, ...
