# Tag Info

### Why wouldn't this perpetual motion machine work?

The water will just sit at an equilibrium level with the horizontal pipe on top half filled. And even if the water was moving, viscosity will slow it down over time and the system will lose energy to ...

### Heat and thermodynamical equilibrium

It is neither. Heat is energy transfer due solely to temperature difference. In other words, heat is energy in transit. What you are describing is internal energy, specifically, internal molecular ...
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### Why wouldn't this perpetual motion machine work?

In the picture in the question the water level in the pipe on the right is higher than in the main container. This makes the pressure at the bottom of that pipe higher than in the main container, so ...
• 52.2k
Accepted

### Derivation of Saha equation through "volume accessible to electrons"

After thinking a lot, it came to me the idea that it's all about a statistical effect of electron distribution. Let's take the number of energy levels $g_s$ around an energy value and evaluate in how ...
Accepted

### How non-$PV$ work is handled in thermodynamic identities?

There is no exact formula for $W_{other}$ - it's an umbrella term. For instance, it could include other types of mechanical work like spring work where $W = \frac{1}{2}k(x_1^2-x_2^2)$ or various types ...
• 6,971

### Thought experiment with specific heat

Now, because the specific heat capacity of the material has been lowered, it can no longer hold all the heat that it previously contained, and so it will radiate heat into the environment. Firstly, ...
• 63.1k
Accepted

### Thought experiment with specific heat

Now, because the specific heat capacity of the material has been lowered, it can no longer hold all the heat that it previously contained Heat capacity tells us how much energy is needed to produce a ...
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### Why wouldn't this perpetual motion machine work?

...since when water drops the pressure inside the container decreases, which makes the water in the pipe ascend. The water rises in the pipe only if the total pressure from the left is greater than ...
• 36.6k
1 vote

### Thought experiment with specific heat

Others have pointed out problems in your specific wording: Heat can't be "held," etc. So just replace "Now, because the specific heat capacity of the material has been lowered, it can ...
• 19.8k
1 vote

### What's the disconnect between blackbodies and lived experience? Do they violate the laws of thermodynamics?

"My understanding of the 2nd law of thermodynamics is, partly that, basically a 'cold' object cannot heat a 'hot' object." That's only true in some situations. This is a problem of over-...
1 vote

### Why wouldn't this perpetual motion machine work?

...when water drops... What would make it drop? Water is, for all practical purposes, incompressible. If water was flowing in the pipe as shown by the red arrows, then the rate at which it flows in ...
• 11k
1 vote

### What's the disconnect between blackbodies and lived experience? Do they violate the laws of thermodynamics?

In order for your 130C body "all by itself" to be "in equilibrium" at 130C, it needs to be in a 130C environment, like a box whose walls are 130C. If it's fully alone in a 0K ...
1 vote
Accepted

### In a polytropic process, how can I prove the validity of this equation: $v_1 = v_2 (\frac{T_2}{T_1})\exp{\frac{1}{1.1-1}}$?

$$PV^n=C$$$$\left(\frac{mRT}{V}\right)V^n=C$$$$TV^{n-1}=\frac{C}{mR}=C'$$
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1 vote

### Chemical equilibrium on phase diagram

Here is how to think about the chemical potential and chemical equilibrium: if the substance can exist at two or more different states, all at the same $T$ and $P$, then the most stable state is the ...
• 2,824
1 vote

### Chemical equilibrium on phase diagram

Outside the coexistence line, only one phase is present at equilibrium conditions. Therefore no chemical equilibrium between different phases is possible. A possible way of describing such a situation ...
1 vote

### Thermodynamics isothermal reversible process

For reversible isothermal process the heat is not zero, it is $$Q = T \Delta S$$ If the process is also isobaric, as in a phase transition, then $$Q = T \Delta S_\text{vap} = \Delta H_\text{vap}$$ ...
• 2,824
1 vote

### What is the force exreted by gas particles per unit area on the walls of the container?

It's pressure. That's what pressure is - it's the definition of pressure. Force, energy, and pressure are different things. They even have different units. You can't say "my room is 12 hours long....
1 vote

### Will the ideal gas equation change if we consider non equillibrium condition and then use kinetic approach and thermodynamic approach?

Thermodynamics is a phenomenological approach - the ideal gas equation is simply postulated (or derived from more elementary laws of Charles, Gay-Lussac and Boyle-Mariotte). In statistical physics the ...
• 52.1k
1 vote

### Will the ideal gas equation change if we consider non equillibrium condition and then use kinetic approach and thermodynamic approach?

The ideal gas equation doesn't change during non equilibrium conditions, it just doesn't apply during non equilibrium conditions. It only applies under equilibrium conditions. Once equilibrium is re-...
• 63.1k
1 vote
Accepted

### Units of the derivative of an exponential function with respect to a quantity with units in the argument?

$$y = \exp\left[\frac{ax}{b+x}\right]$$ where $y$, $a$, and $b$ are dimensionless and $x$ has some physical dimension And there's your problem right there. As @Samuel pointed out in the comments, ...
• 43.7k

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