# Tag Info

## Hot answers tagged thermodynamics

71

Thus, the air molecules contribute a small portion of their kinetic energy to the paddle, which is then expended as heat on the other side of the border, making the air molecules on the left colder, while air molecules on the right heat up. Doesn't this mean a decrease in entropy? Yes it does. However, we need to take the thermal noise of the resistor ...

30

Do black holes violate the first law of thermodynamics? No. See Wikipedia re the first law of thermodynamics: "The first law of thermodynamics is a version of the law of conservation of energy, adapted for thermodynamic systems. The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed ...

4

If you have a glass of water, every molecule of water is under the influence of the gravitational potential field. Each molecule pushes down on the molecules below. The molecules of water near the bottom of the glass experience the downward force from all molecules above them (each molecule transfers the force downward). If you made a hole near the bottom of ...

3

Dr. Robitaille says that blackbody radiation is not universal, even inside cavities where the surfaces are all at thermal equilibrium. That is highly controversial since the electromagnetic fields in a cavity are usually considered as an additional substance, called a "photon gas" which is also at thermal equilibrium and hence has a temperature. This ...

3

A neutron has an up quark with charge +2/3 and two down quarks each with charge -1/3. It has a magnetic moment and it does interact with electromagnetic radiation. So the premise seems incorrect.

3

As it was explained in one of Halliday's books, the reason is that the black dress heats the air inside it up, thus causing a continuous flow of air in between the skin and the dress. The cold air flows in from below, gets heaten up, and gets out from above, providing a continuous ventilation.

2

The Maximum Entropy principle, principally popularized by Jaynes, is known by most people having studied statistical physics. The way I see it, although Jaynes considered it as crucial in the foundations of equilibrium statistical mechanics and other people in the field still do (like Roger Balian for instance), it is more taught and thought of as a useful ...

2

The burning fuel/air mixture generates a lot of heat, which greatly increases the temperature and pressure inside the cylinder. The high pressure gases then push the piston down, providing expansion work that turns the crankshaft. Some of the heat from this process transfers into the water jacket of the engine, where circulating water (from the water pump) ...

2

If I'm not mistaken, a similar effect happens near all sufficiently cold bodies: moisture from the air condenses and becomes visible when cooled from room temperature, a process similar to cloud formation. The reason it stops forming after some time, near ice cream or otherwise, is because the object gradually warms up to room temperature. If the foggy layer ...

1

I'll assume this problem is continuous as it makes sense on physics, and not discrete as you wrote on your pseudocode. Its worth pointing out, it makes a huge difference if the problem is discrete or continuous, as I have explained in the comments. However, one can also write a pseudocode for the continuous problem as well: HEATING = 1 # degree per minute ...

1

Certainly, you agree $dH=C_P dT$ if we're at constant pressure. If $H$ and $C_P$ don't actually depend on pressure, then you can use this equation regardless of whether pressure changes. However, to determine $C_P$ and $H$ you first need an equation of state (such as $PV=NkT$). Without knowing the specific equation of state (aka, if your gas is ideal or ...

1

Options: Your dish is not actually as cold as you think it is: verify with a thermometer that the dish is actually colder than ambient temperature. Your hand is a terrible thermometer because it does not reach thermal equilibrium with the object you are trying to measure, and so it is sensitive to the thermal conductivity of the substance you are touching. ...

1

I can’t write this computer simulation for you (at least not based on the data provided) but will instead explain a few basic relationships that govern the heating and cooling of objects. I hope this helps. Consider a building an object that is composed of $n$ objects of masses $m_i$ with specific heat capacities $c_{p,i}$, then the building has an overall ...

1

Thermal diffusivity is the ratio of heat conduction ability to heat storage ability of a material at constant pressure. A high ratio indicates that the material will conduct heat away more readily than it can retain the heat. A low ratio indicates that the material has a great capacity to store heat, and will not be able to conduct heat away as rapidly. ...

1

A force does not require a constant input of energy to exist. Energy is only required to perform work, which is exerting a force over a distance. $$W = \mathbf F \centerdot \Delta \mathbf x$$ That distance is key. In your example, if the size of the container does not change, no energy is expended no matter how long the force lasts. If the force is used ...

1

A vacuum will offer you no advantage in cooling your aluminum block, ceteris paribus. In a vacuum, the only method of heat transfer is radiation. You will lose the benefit of any of the other three methods listed below. There are four ways for an object to lose heat: (1) Conduction - Thermodynamic energy is transferred through physical contact with ...

1

No, it does not. If it did, then it would not curve spacetime and it would not be a black hole.

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