# Tag Info

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Does boiling water really heats room faster than just gas stove? Frankly, I don't think there is a simple answer as it depends on just what the rate of "heating the room" means and the many variables associated with that question. As you can see from the answers by @BowlOfRed and @probably_someone, some clarification may be needed in your question. For ...

2

This really depends on what is meant by "heat the room". Both events will deliver the same amount of thermal energy into the room. But they may be felt by an inhabitant in different ways. Heating an object (like a pan of water) may well feel warmer. The object can radiate heat for a period of time and that radiation could be noticed by someone walking ...

4

Boiling water involves breaking the intermolecular hydrogen bonds that hold water in a liquid state. The energy that this takes is called the heat of vaporization, and, importantly, the water's temperature doesn't increase while it's boiling. You're effectively using some of the heat from the gas stove to break bonds, something that doesn't increase the ...

5

If you have heat, you have "random" movement of different molecules in your material. When two different molecules with different velocity vectors interact, they sometimes emit a photon carrying away some of their energy. This results in the relative kinetic energy of the two molecules being reduced (due to conservation of energy). This average relative ...

-2

This can be understood easily: If your temperature is higher than the surrounding temperature heat will flow out to the surrounding. It is analogous to electric current which moves from a higher potential to a lower potential. Similarly heat current flows from high heat potential(high temperature) to a lower heat potential(low temperature)

1

In the present epoch the universe is a long way from thermal equilibrium. It consists of a large number of isolated hot spots (a.k.a. stars) in a sea of background radiation which has an average temperature of just $2.7$ K. But stars have finite lifetimes (although this can be a very long time for white dwarf start) so eventually all the stars in the ...

9

Everything that is not 0 Kelvin radiates electromagnetic energy. In vacuum, this is the only relevant form of heat transfer. The hotter you are, the more energy you radiate (I believe the relevant equation is given here). The question whether you cool off or heat up in space depends on whether you absorbs more electromagnetic radiation than you give away. ...

42

You exchange heat with the objects around you. If the objects around you are hotter than you, you'll heat up. If the objects around you are cooler than you (neglecting the heat you're generating due to metabolic processes), you'll cool off. In space, the objects around you (mostly interstellar medium) is cooler than you so you radiate more heat away from ...

0

For main-sequence stars, the Luminosity is related to the temperature by the expression $L\approx M^{3.5}$. The reason for the 3.5 exponent is because the relationship best fits some stars at $L = M^3$ up to $L = M^4$. For non-main-sequence stars, you probably need a relationship between density and Luminosity.

0

I humbly disagree with the majority of the other answers here. It can be very useful and make lots of sense to talk about the temperature of a single particle. You just need to realize that it's not quite the same (although it's pretty darn close) as the temperature defined by physicists in typical statistical mechanics and thermal physics studies. ...

1

Yes. I find the best way to think about it is that, when a metal object is heated, all of its dimensions increase as it expands (assuming its not being constrained externally somehow, has isotropic material properties, etc.). So, hole diameters increase and wall thicknesses will increase.

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If a material expands when the temperature is increased this means that the average separation between atoms has increases. So with an increase in temperature across a radial line the atomic separation has increased which means that the thickness of the cylinder has increased.

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I have tried to follow your sequence. It was not clear to me from the description if at the end you were bringing B together with C before or after they each were each in contact with A. But it turned out not to matter as either way heat will flow from C to B. If I followed you correctly, the sequences are as shown in the diagram below. The equilibrium ...

4

This is because the thermometer tube it is contained in is so small in diameter that surface tension effects dominate over gravity and inertia effects. If you were to smoothly increase the diameter of the thermometer tube, there would come a critical point at which for that diameter, tilting the tube would cause the mercury to run out of it.

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Because the question being asked is Why/How does filling a compressed air cylinder produce heat? The conventional answer is that because there are more gas molecules being forced into a confined space there are more gas molecule collisions and with more collisions comes an increase in friction and thus the cylinder heats up. Now when we are filling a ...

1

The internal energy per unit mass (the specific internal energy) of a solid is proportional to temperature. The total internal energy equals the internal energy per unit mass times the total mass. Increasing the volume (and thus the mass) of the a solid, in the absence of any heat transfer from the surroundings to the solid, or a black body that generates ...

1

I think your confusion is that a condenser does not cool to ambient temperature, it cools to saturated conditions. The water needs to be subcooled before it enters the pump, but it is still at relatively high temperature and pressure. There is another loop that cools the condensor. This third loop is usually connected to a cooling tower, lake, or river. ...

0

Tl;dr: Can fusion be achieved only by speeding up particles to high enough speeds to smash into each other? Yes, there is a fundamental limit that needs to be crossed, the coulomb barrier. That requires a certain amount of energy, and the traditional solution is to heat it up until the average velocity is high enough to cross this barrier at a reasonable ...

0

À heat engine is a device for converting heat energy into mechanical energy. Conceptually, the situation can be seen as interacting perfectly elastic spheres, like billiard balls. An accurate description of the system would involve Van der Waals forces, internal degrees of freedom for poly atomic gases and quantum effects but all these are secondary to the ...

-1

You can start with water at $0^{\circ} C$, as suggested in Vibert's answer, measure the height of water in the container, and start heating the water. The density of water at $0^{\circ} C$ is $1 g \cdot cm^{-3}$, at $65^{\circ} C$ it is $0.981 g \cdot cm^{-3}$, at $70^{\circ} C$ it is $0.978 g \cdot cm^{-3}$. So if at $0^{\circ} C$ the height of water in the ...

1

Assumptions: we have a volume of water $(v_1)$ at $100^{\circ} C$ (boiling water) we have a volume of water $(v_2)$ at $20^{\circ} C$ (tap water) we want a volume of water $(v_1+v_2)$ at $70^{\circ} C$ the pot that will finally hold the $70^{\circ} C$ water will consume a negligible amount of energy from the water (generally a bad assumption. Might have to ...

1

It would be great if you guys could provide some relevant thermodynamics formula related to cooling rate which can be applied to this scenario of cooling a cup. The 'go to' Law for this kind of cooling is Newton's Cooling Law: $$\boxed{\frac{\text{d}Q}{\text{d}t}=-hA\Delta T}$$ where: $\frac{\text{d}Q}{\text{d}t}$ is the heat energy loss per unit of ...

2

Is the person touching the sun? conduction needs contact of solids. Convection is when a fluid is moving in bulk brings changes in the ambient temperature, as the wind does. The temperature of the atmosphere depends on convection and indirectly the persons living in this atmosphere. The sun is a ball of plasma millions of kilometers away and its ...

2

[question 3] Was there really no way to keep the craft from irradiating everything on its path? from the article "It was proposed that after delivering all its warheads, the missile could then spend weeks flying over populated areas at low altitudes, causing secondary damage from radiation" thats messed up... I have seen this claim in many places, ...

3

Could someone explain how this type of critical state does not result in a huge nuclear explosion? In general, you have three possible states for a lump of fissile material: Subcritical, in which there is no chain reaction (i.e. the material decays essentially as if it were just a bunch of separate individual atoms); Critical, in which there is a sustained ...

0

temperature of a substance was a measure of the average kinetic energy of the particles in that substance This is only true for a monatomic gas. Even without quantum mechanics, a classical diatomic gas has three more degress of freedom than a monatomic gas—two rotational and one vibrational—for a total of 6. The equipartition theorem tells us ...

3

Let us consider a situation where we put one "blue" molecule in a gas of "red" molecules. We allow it to equilibriate with a heat bath of temperature T. In this context the "blue" molecule is certainly a single classical particle and it can be associated with a temperature. The important point here is what information do we know about the "blue" particle, ...

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I know that macroscopic temperature is a measure of kinetic energy of particales at very low scales (let's call it microscopic kinetic energy). This is not generally true. The only case where this is true is for an ideal monoatomic gas. For all other materials there are more internal degrees of freedom than merely the kinetic energy. For the remainder of ...

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The macroscopic kinetic energy of a system of particles is the kinetic energy due to the velocity of the center of mass of the collection of particles with respect to an external frame of reference. For example suppose you have a container filled with an ideal gas. The temperature of the gas is a measure of the average kinetic energy of the randomly moving ...

5

Thermal energy is the energy contained in the internal degrees of freedom of a system, so there are two problems with saying that the KE of a single particle gives its temperature. First, the system’s overall momentum, angular momentum, and so forth are by definition external degrees of freedom. Since they are external then by definition they are not ...

1

One can achieve fusion without high temperatures. However, one cannot achieve net energy production using fusion without high temperatures (based on current knowledge). You consider fusion using accelerated ions. It is possible, but, as niels nielsen wrote, inefficient: in two colliding beams, most ions will undergo Coulomb scattering, not fusion. Another ...

0

The reason for this unexpected behavior is the density of the hot water is lower than the cold water and so the hot water floats over the cold water. Even after the color already been mixed and, even after I mix the water a hot water concentration will be created on the top layer. Check this video that proves the density point.

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The "easy" way to get a bunch of particles moving very fast is to make them very hot. If they are hot enough, some of them will fuse when they collide. While it is possible to speed the particles up in an accelerator/collider instead, and then smack them into each other, this is a hugely inefficient enterprise. The energy release upon fusion is tiny ...

2

Thermoelectric effects, the Seebeck potential. But in metals it is very small, because temperature does not have much effect on the kinetic energy of the electron gas. It is much larger in doped semiconductors, where the electrons can be treated as a classical Drude gas.

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