# Tag Info

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Your body’s circulatory system is removing heat from your hand inside the oven mitt. This makes your whole body act as a radiator to dissipate the slight temperature increase in your hand and keep the temperature from rising too much inside the mitt. The mitt acts as an insulator and slows the heat transfer into your hand to a rate that can be radiated by ...

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I'm not entirely convinced you will be holding the pan long enough for the mitts to actually reach the same temperature as the pan, and I'm not sure you could hold it indefinitely, but let's ignore that here. This is because the cloth is an insulator and doesn't allow as large a heat transfer as if I held the object with my bare hands. It's still this ...

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You can't "perpetually" hold a hot pan with oven mitts without burning your hand. The issue is how long it will take. Oven mitts enclose a lot of air, whose thermal conductivity is low, and are thick, also lowering the flow of heat. If the heat flow is ~10000x less than it would be, for example, through a piece of aluminum foil, it may seem like ...

9

What a great question! You are asking a question about the subfield of transport phenomena and so it can be worthwhile to have some models. So the first thing is linear heat flow, when you make contact with a surface there is a parameter $c$ such that the heat transfer is $p~(T_{\text s} - T_{\text{you}}).$ Heat is a flow of energy which is a conserved ...

3

No, the combination releases enough energy to heat the surroundings enough that the entropy increases.

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Note: Was going to comment on @Nuclear Wang's answer, but Without the 50 reputation yet, I'd like to build off their example of living organisms being a local system with a decrease in entropy, and how this is balanced out. As @Nuclear Wang pointed out about living organisms: But although they can reduce entropy locally, they must increase the entropy of ...

2

When the container is open to atmosphere, gasses may exit or enter. This keeps the pressure inside equal to the pressure outside. this also keeps the volume of the gas inside the container the same unless the container itself expands or contracts. I believe that the statement should have been clearer on these points.

2

The partial pressure is the pressure, produced by a certain constituent gas in mixture of gases, if it occupied the whole volume. This notion makes sense only for ideal non-interactings cases, for which Dalton's law is valid - https://en.wikipedia.org/wiki/Dalton%27s_law. For those : $$p_{total} = \sum_i p_i$$ In case of interactions, substances will ...

2

The heat transfer $\dot{Q}$ ($\mathbf{Watt}$) flowing from the hot pot to the cool water is given by Newton's Law of Cooling: $$\dot{Q}=UA\Delta T(t)$$ where: $A$ is the contact surface area between pot and cooling water, $\Delta T(t)$ is the difference in temperature between the food in the pot and the cooling water surrounding it (both evolving in time $t$...

2

There are two heat transfer resistances involved here: the heat transfer resistance outside, from the surrounding fluid to the surface, and the heat transfer resistance inside the object, from the surface to the internal region. Newton's law assumes that the overall resistance is dominated by the outside resistance (which is typically nearly constant). ...

2

tl;dr– Your hand's cooling the cloth while the hot-object warms it. The cloth will have internal temperature variation. A common steady-state assumption is constant heat flow, where your hand sinks as much heat as the hot-object gives off. However, I presume that eventually the cloth will reach the same temperature as the object in question when it ...

2

So why can I perpetually hold, say, a hot pan with oven mitts without burning my hand? Before attempting to answer this question, we need to be able to answer the question "how hot does something have to be to cause a skin burn injury?" The answer is it depends on the combination of the temperature of the surface of the skin that results from ...

2

Not just conduction the same amount of heat must be transferred from the object to my hand as before. No. The hot pan, when held in the air, will indeed reach ambient temperature after enough time. But to do so, the thermal energy can either be transferred: to your hand, via conduction to the ambient air, via convection to the nearby objects, via thermal ...

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You are right that the "maximization of entropy" is not the cause of anything; entropy is an emergent phenomenon, meaning that it is a result of the behavior of an underlying system, in this case some collective. The power of the concept "entropy" is that it is independent of the underlying "substrate" — all collectives follow a ...

2

Yes, it is, but it is, indeed, as you say, "extremely unlikely" in a very specific sense. To the best of our knowledge, there is nothing at all to prevent the atoms and molecules in the Earth from all moving to conspire "just right" so that at a particular point in time, they give it a huge "kick" that sends it reeling. Such ...

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You seem very confused about how to apply the first law of thermodynamics to this system. First of all, the system is not isolated. It is receiving work from its surroundings. If the gas is the system, then its surroundings is the piston (and that is what is doing the work). For an essentially massless, frictionless piston, the work done by your hand on ...

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A jack with hydraulic oil in it will have a very slight pressure difference from the top to the bottom due to pressure increasing with depth. This is negligible to the operation of the jack. For instance, a typical hydraulic jack with a load on it may have around 1800 psi at the top of the cylinder, and around 1800.4 psi at the bottom, depending on its ...

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So, doesn't specific heat capacity of a material affect the rate of heat transfer/flux ? It does: just look at Fourier's equation of heat conduction: $$\frac{\partial T}{\partial t}=\alpha \Big(\frac{\partial^2 T}{\partial x^2}+\frac{\partial^2 T}{\partial y^2}+\frac{\partial^2 T}{\partial z^2}\Big)$$ where $T$ is the temperature and: $$\alpha=\frac{k}{\rho ... 1 For the overall heat exchanger, the rate of entropy flowing out minus the rate of entropy flowing in must equal the rate of entropy generation within the exchanger. This must be greater than zero in order to satisfy the 2nd law of thermodynamics. 1 Your assessment for an open system operating at steady state is correct provided that you add or remove the exact amount of heat necessary for the exit pressure of the gas to exactly match its inlet pressure. The gas not being an ideal gas is irrelevent. The change in enthalpy being equal to the heat added is correct only for an isobaric process in a closed ... 1 Internal energy, pressure and volume are all state properties. A cycle returns all properties to their original values. So the change in each of these is zero. Enthalpy is defined as$$H=U+PV Therefore it too is a state property so its change is also zero. Work and heat are energy transfers and are not properties. They depend on the processes carried out ...

1

By steady state, I presume you mean the condition under which no heat is being transferred in the system? This will only occur when both cloth and object reach the temperature of the surrounding air. Before then, the cloth loses heat to the air while it is gaining heat from the hot object. Presumably at least half of the cloth's surface area will be directly ...

1

With a hydraulic jack, the weight of the object being lifted is usually much greater than the weight of the working liquid. Therefore the difference in pressure in the working liquid due to different heights will be much smaller than its absolute pressure, and may be difficult to measure. To expand my answer, in a hydraulic jack you apply a relatively small ...

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In "The Principles of Chemical Equilibrium," by K.G. Denbigh, in section 2.4 discusses, in a very precise way, how this applies to (a) a closed system at constant temperature and pressure and (b) an open system operating at steady state in contact solely with a constant temperature reservoir. In the former case he discusses a specific example of ...

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