Tagged Questions
0
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0answers
44 views
Air pressure in balloon
I have to calculate the air pressure inside of an hot air balloon. After some searching I found out that I can use the ideal gas law: PV = nRT (from Wikipedia)
So to get the pressure in the balloon I ...
0
votes
1answer
679 views
Beginner Thermal Dynamics Question [closed]
A syringe is set up filled with air (mainly N2 and O2) as shown in the diagram below. The surface area of the syringe is 15.3 cm2. The initial pressure inside the syringe is Pi = 114 kPa and the ...
1
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0answers
27 views
Calculating the change in entropy in a melting process
I have a homework question that I'm completely stumped on and need help solving it.
I have a $50\, \mathrm{g}$ ice cube at $-15\, \mathrm{C}$ that is in a container of $200\, \mathrm{g}$ of water at ...
0
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1answer
44 views
Calculating the coefficient of thermal expansion in liquid
I am trying to write a matlab function that calculates the coefficient of thermal expansion of water from a given temperature. From what I understand the thermal expansion coefficient is calculated as ...
1
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0answers
43 views
What defines the adiabatic flame temperature?
In a case, I have to solve, I need to describe the combustion of natural gas (Groningen natural gas to be more specific). However I am having some problems understanding the adiabatic flame ...
-1
votes
0answers
23 views
Finding rms velocity in isothermal process [closed]
I think none of these options are correct, I just need someone to confirm. Please, as no option is matching with $V_{rms}$.
0
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1answer
18 views
Gas transformation for different molar number
When a gas at normal conditions (1atm, 273K, 22.4L) we say like the $$\frac{PV}{T} = 0.0820...$$
And by the know equation: $$PV = nRT$$
Where R is equals to $0.08205...$ and $n$ is the number of mols ...
0
votes
1answer
46 views
What is the coefficient $\mu_\text{air}$?
I am answering some exercises in thermodynamics, and I am still in trouble with some values and constants.
In the exercise, it is given: $\mu_\text{air}=1.8\cdot10^{-5}~\text{kg/m s}$. What for is ...
1
vote
1answer
33 views
How can I find the temperature of this system?
A system was given a small amount of thermal energy dE, and its number of states G grew by 25%. How can I find the system temperature?
The system contains gas particles, I know that $dE << ...
1
vote
0answers
18 views
Henry's Law in metals
For fixed temperature the concentration of a gas dissolved in a solution is directly proportional to the gas pressure $p$, i.e. $c_s (T,p) = f(T)p$. Since $H_2$ only dissolves in metals as single ...
0
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0answers
92 views
What is the condition for getting Bose-Einstein condensation? [closed]
Consider an ideal Bose gas in three dimension with energy-momentum relation E proportional to $p^s$ with $s>0$. Find the range of $s$ for which this system may undergo a Bose-Einstein ...
1
vote
1answer
62 views
Maximizing Multiplicity of Einstein Solid == (Temperature = $\infty$)?
If I have a system consisting of 2 Einstein solids (A and B) is it equivalent to say that maximizing the multiplicity of the ...
0
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2answers
66 views
Is it possible to “add cold” or to “add heat” to systems?
Amanda just poured herself a cup of hot coffee to get her day started.
She took her first sip and nearly burned her tongue. Since she didn't
have much time to sit and wait for it to cool down, ...
1
vote
1answer
90 views
Joule-Thomson effect of Van der Waals gas
I'm supposed to calculate the inversion pressure $p_i$ of a Van der Waals gas. The state equation of the Van der Waals gas is: $$(p + \frac{a}{V^2})(V-b) = RT.$$ To get a hold of the inversion ...
2
votes
2answers
126 views
Hot Air Balloon and Buoyancy
This is a conceptual question in a solution I am trying to understand.
Problem statement:
I have a balloon with a volume of V $m^3$. The outside air temp is $K$ kelvin
and mass to lift is $m$ kg.
I ...
1
vote
1answer
56 views
How long does it take a warm object to cool in air?
This is a work-related question. A warm steel torus of a given diameter & thickness is left in a room held at a controlled temperature, how long does it take to reach equilibrium? Assume the air ...
0
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0answers
36 views
Relation for Temperature and Pressure starting from chemical potential
Assume we have a system filled with a specific substance. Inside the system there is a small box with an opening. Usually this would mean $T,p,\mu$ would all be the same inside the box and outside. ...
1
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0answers
30 views
What is the meaning of $h_L - h_H$ for a heat engine?
My problem gives me a Carnot cycle heat engine with water as its working fluid, with $T_H$, $T_L$, and the fact that it starts from saturated liquid to saturated vapor in the heating process.
I need ...
0
votes
1answer
56 views
In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
Say I have an ideal gas that has a known $P_1$, $P_2$, $T_1$, and $T_2$ undergoing a reversible adiabatic process. I want to find the work done so I must use $PV = RT$ to get the change in $V$, so ...
1
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0answers
76 views
Rotational Constant and Moment of Inertia of Fluorine gas
I have come across some homework question on thermodynamics which needs me to calculate $B$ of $F_2$
My attempt:
$B= \frac{h}{8\pi^2cI}$ where $I=\mu r^2=\frac{m_1m_2}{m_1+m_2} r^2$
Atomic mass of ...
-1
votes
1answer
88 views
Sensible heat question (solving for temperature)
If $55 034.175 \rm{kJ }$ of heat are transferred to $150 \rm{kg}$ of ice at a temperature of $-12.15 ^\circ \rm{C}$, calculate the temperature of the resulting water.
Using $Q = mc(t_2-t_1)$ or ...
2
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1answer
76 views
Rate of Cooling
I was given the following problem:
Two objects have a temperature difference of 20 degrees C at time 0. Two minutes later, they have a temperature difference of 18 degrees. How long does it take ...
-1
votes
1answer
73 views
Sketch p-v and t-v diagrams [closed]
I have been trying to sketch this diagram for the thermodynamic cycle below but I'm not sure how to go about it. Any help is appreciated.
Sketch the cycle below on p-V and T-V diagrams, showing shape ...
0
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0answers
34 views
State equations in magnetic systems
Assume there is an isotropic magnetic material in a homogeneous field $\vec{H}$ inside of a long coil. The work done to the material is given by $\delta A = H dM$, where $M$ is the magnetisation of ...
1
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1answer
81 views
Thermodynamics and electromagnetic fields
The energy density in an electromagnetic field is given by: $u = (1/2) <\vec{E}^2 + \vec{B}^2>$ where $<,>$ denotes the average over time. In a cavity it holds that $u= u(T) = ...
1
vote
1answer
75 views
A simple thermodynamic question? [closed]
I tried this question a lot of time and few day's earlier I also solved it correctly but I don't know why I am not able to solve it now. I can't get what link I am missing.
ques: 2 moles of helium gas ...
5
votes
1answer
180 views
Thermo homework (HW) problem
I do not believe this question can be solved with the thermodynamics knowledge that I have learned thus far, but someone correct me if I am wrong:
A 0.2-m³ tank containing helium at 15 bar and ...
0
votes
0answers
56 views
Uniqueness of adiabatic curve [closed]
Prove that for any thermodynamic system in the quasi-static process, two adiabatic curves on a P-V diagram cannot intersect.
1
vote
1answer
74 views
Thermodynamics of a bar, specific heat
I have a problem and I don't understand how the book solves it. It says I have a bar such that $$F=aT^2(L-L_0)$$
where $F$ is the force or tension of the bar, $T$ is the temperature, and $L$ the ...
3
votes
3answers
190 views
Irreversible process
I have this problem. I have an ideal gas that goes through an irreversible adiabatic decompression. I have the initial state (P,T,V), and the final pressure, and I have to calculate the entropy ...
1
vote
1answer
217 views
Constant pressure and temperature mixing of 2 different ideal gases - possible work and heat?
A simple question I hope...
Initially, have two separate containers of 2 different ideal gases, 1.) N1, P, T, V1 and 2.) N2, P, T, V2.
After mixing, the pressure and temperature are still P and T, ...
1
vote
0answers
31 views
Heat contained in compressed gas [closed]
I am trying to compute the amount of energy released in the form of heat if I compress 1 cubic meter of Hydrogen to 0.1 cubic meter while submerged in a large body of water of a given temperature - ...
0
votes
0answers
79 views
Linear Expansion and superficial expansion [closed]
An iron tyre of diameter 50 cm at 15 deg C is to be shrunk on to a wheel of diameter 50.35 cm. To what temperature mist the tyre be heated so that if will slip over the wheel with a radial gap of 0.5 ...
0
votes
0answers
33 views
Thermal Physic ($\lambda$) and ($C_p$) calculation for multilayer wall [closed]
I would like to know, how could I calculate the Thermal conductivity ($\lambda$) and heat specific ($C_p$) of Multilayer wall? (I have a wall with 9 layers which are included wood and air)
0
votes
0answers
72 views
Find out the temperature using linear expansion co-efficient [closed]
The coefficient of linear expansion of iron is .0012 / C(I know this isn't). At what temperature a 21 meters long iron rod(measured at 0C) will exactly fit a case which is 22 meters long?[Neglect the ...
5
votes
3answers
207 views
experimental technique for measuring temperature of an ant
I am taking a course on thermodynamics. I have a question from my text(halliday & resnick,physics-1). They asked me to measure temperature of an ant or an insect or a small body,like a small ...
1
vote
3answers
912 views
Internal energy according to the van der Waals equation
I am trying to derive the internal energy of a gas which obeys the van der Waals equation.
I have however encountered some problems. I calculate the integral of $dU$ from $V=0,T=0$ to $V=V, T=\infty$ ...
0
votes
0answers
58 views
Using thermodynamics and Kinematics together to solve a parachuter problem?
I need to find a parachutist's displacement after a given height (nearly 37000m) and at a given latitude. I have his mass, area, parachute area, drop height, parachute deployment height, data about ...
1
vote
1answer
67 views
Thermodynamic process when nebula is heated
The basic thermodynamics problem is stated as follows.
The nebula contains a very tenuous gas of a given number density (atoms per volume) that is being heated to a given temperature. What is the ...
4
votes
2answers
202 views
Is the proper interpretation of temperature missing in this book?
In Randall T. Knight’s textbook “Physics for Scientists and Engineers” in the first chapter on thermodynamics (Ch. 16: A Macroscopic Description of Matter) one of the first conceptual questions is ...
0
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1answer
205 views
Expressions for canonical partition function and probabilities $p(E_i)$
Given an atom with 4 allowed states corresponding to the energy levels
$E_1 = 0$, $E_2 = E$, and $E_3 = 2E$ with degeneracies 1, 1, and 2 respectively.
How do I find the expressions for the ...
1
vote
2answers
41 views
thermodynamics in air and water
In perspective of thermodynamics,a person can survive a temperature of twenty degrees Celsius in air, but a person cannot survive in water with same temp.(it's not because he can't breathe) why is ...
2
votes
1answer
207 views
What is non-thermal plasma?
I read about non-thermal plasma, but I still have some questions:
The ions and neutral particles are not in thermal equilibrium with the electron, does that mean that the overall temperature is low ...
0
votes
1answer
459 views
Heat Exchanger Calculation
I have a tank of oil at 55 degrees c. I plan to run a copper pipe 8mm in diameter (1mm thickness) into a coil 15m long inside the tank. For all purposes of assumption, the copper pipe is perfectly ...
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votes
1answer
96 views
I need help with this question on Heat Capacity
A calorimeter has a Heat Capacity of $70 J/K$. There is $150g$ water with a temperature of $20^oC$ in this calorimeter. In this, you put a metal cube of $60g$ with a temperature of $100^oC$. The ...
1
vote
0answers
168 views
Simple heat transfer question [closed]
You add an unknown volume of milk of $5.2 ^\circ C$ to a cup of coffee ($40 mL$ of water, temperature: $80.3 ^\circ C$). After a while of stirring the temperature reaches $73.2 ^\circ C$. The ...
2
votes
2answers
786 views
Calculating work done on an ideal gas
I am trying to calculate the work done on an ideal gas in a piston set up where temperature is kept constant. I am given the volume, pressure and temperature.
I know from Boyle's law that volume is ...
1
vote
1answer
362 views
Adiabatic expansion [closed]
I'll start off by saying this is homework, but I ask because I don't understand how the math should work (I don't just want an answer, I'd like an explanation if possible). I understand if this is ...
0
votes
1answer
1k views
Work Done by an Adiabatic Expansion
I am given the information that a parcel of air expands adiabatically (no exchange of heat between parcel and its surroundings) to five times its original volume, and its initial temperature is 20° C. ...
2
votes
1answer
588 views
Work Done in an Isobaric Process
I am given the information that an air parcel undergoes isobaric heating from 0° C to 20° C, and that's all I'm given. I have to determine the work done by the parcel on its surroundings. I know that ...
