What is Temperature: Definition and 999 Discussions
Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is colder or hotter.
Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have used various reference points and thermometric substances for definition. The most common scales are the Celsius scale (formerly called centigrade, denoted as °C), the Fahrenheit scale (denoted as °F), and the Kelvin scale (denoted as K), the last of which is predominantly used for scientific purposes by conventions of the International System of Units (SI).
The lowest theoretical temperature is absolute zero, at which no more thermal energy can be extracted from a body. Experimentally, it can only be approached very closely (100 pK), but not reached, which is recognized in the third law of thermodynamics.
Temperature is important in all fields of natural science, including physics, chemistry, Earth science, astronomy, medicine, biology, ecology, material science, metallurgy, mechanical engineering and geography as well as most aspects of daily life.
In case of adiabatic process, we all know that the relation between temperature and pressure and that's given below:
P. T(γ/(1-γ)) = Const.
therefore, P = Const. T(γ/(γ - 1))
or, ΔP = Const. (γ/(γ - 1)).ΔT(1/(γ - 1))
It's just an attempt to find out the relation. Don't know how much correct I...
I can visualize gas molecules, contained in a vessel, randomly bouncing into each other. As temperature increases, the collisions occur more rapidly. I suppose this also applies to liquids. I'll guess that a liquid's boiling point is where the molecular collisions become so violent that...
Well... that: Please, could you please assist me in obtaining a rough estimate of the distance from the Sun at which a planet resembling Venus or a hypothetical Venus-like planet (for the sake of simplicity) would have a habitable-zone surface temperature? A "back-of-the-envelope" educated...
My main question here is about how we actually justify, hopefully fairly rigorously, the steps leading towards converting the sum to an integral.
My work is below:
If we consider the canonical ensemble then, after tracing over the corresponding exponential we get:
$$Z = \sum_{n=0}^\infty...
For this problem,
The solution is,
However, why must we use absolute temperature for the ideal gas law (i.e why can we not use Celsius for T)
Many thanks!
My first assumption is that the temperature dependence on the mobilities can be neglected, and so we would have:
$$R_H(T)= \frac{1}{e} \frac{p_v(T)\mu_h^2-n_c(T)\mu_e^2}{(p_v(T)\mu_h+n_c(T)\mu_e)^2}$$
The expression for the electron and hole densities could be derived from...
Hello everyone,
I deposit a thin film of HTM based carbazole and I measure the PL at lower tempertaure . by fiiting the experimental results with 5 peaks . I notice the dissapering of peak 1 at 300K and peak 3 at 200K. What is the nature of the interaction that can occur at lower temperature of...
FIGURE 5 shows an electrically heated oven and its associated control
circuitry. The current, I, to the oven's heating element is fed from a
voltage-controlled power amplifier such that I = EK1. A voltage, VD, derived
from a potentiometer, sets the desired oven temperature, TD. The oven...
(a)
I know some of the apparatus needed for the experiment, such as DC power supply, ammeter, voltmeter, maybe rheostat. But I don't know how to change the temperature of diode. What is the correct and safe way to change the temperature of diode?
Thanks
How to correctly determine the temperature of electrons in an ion source based on ECR?
Is it possible to use the Saha equation?
##\frac{n_en_i}{n_a}=\frac{g_eg_i}{g_a}*3*10^{21} T^{3/2} e^{-J/T}##
Using the search, I found the McWhirter criterion for the applicability of the formula above:
##n_e...
As part of our UG curricula in Physics major, we have a practical in which we have to draw the calibration curve of an NTC ##10~\mathrm{\Omega}## thermistor, and then construct a circuit to maintain the temperature of a water bath.
The calibration curve of our thermistor. The Prof. said that...
Usually, the mental image of temperature is: an internal property of a bulk of matter, which typically describes the average kinetic plus rotation/vibration energy of molecules, so we imagine a gas in which temperature is a measure of how quick molecules are, and how frequently they collide one...
Looking at the given values, I thought the specific heat formula could be used to calculate the final temperature of the air: c = Q/mΔT. Since the final temperature is the sum of the initial temperature and the change in temperature, the formula can be rearranged to ΔT = Q/m*c.
Q = 30 W * 10 s...
An insulated container (constant volume, adiabatic) contains an Ideal gas with pressure P1 and temperature T1.
We open the container's hatch for a few seconds and let some particles escape from the container, then we close the hatch again. We know container's pressure has reduced by exiting...
For this problem,
The solution is,
I understand their logic for their equation, but when I was trying to solve this problem, I came up with a different expression:
##\Delta A = \Delta L_x\Delta L_y##
##\Delta L_x =\Delta L_y = \Delta L## since this is a square.
##\Delta A = \Delta L^2##...
I have the following task and I am not getting anywhere:
A steel tank with 15 m³ volume, well insulated from the outside, contains air at a temperature of 288 K and a pressure of 1 bar. It is connected to a compressed air line via a valve that is initially blocked. which constantly supplies...
Hello everyone, since several weeks, no response from the other forums, I tried to compute a simple model for a greenhouse in a garden. First idea was to compute mass transfer, Navier-Stokes and heat equation all together but in my knowledge no analytical solution exists.
I need to build a...
I have a cube with a volume of 1000m3 at an initial temp of 290K. The bottom side (10m by 10m) is open to the ambient air. I put this cube into a huge fridge and cool the whole volume by 5K. I close the open side by placing a cover on it. This cube has now got a volume of air at a temperature of...
I am a high school student and recently I have been working on a project about how temperature affects the frequency of a string emits. I have read blogs like https://www.physicsforums.com/threads/tension-and-frequency-with-change-in-temperature.833185/ and completed the part of thermal...
When I try P_rel_e = P_ideal I couldn't get a single number that is close to the given T_Max. It might be that I used the wrong equations but I am not sure. Can anyone give me some guidence on this question?
The commonly called value of the temperature at recombination is 3000 K.
According to this reference the process of recombination can be described by the Saha equation:
3.1. Recombination and the formation of the CMB
Recombination happens quickly (i.e., in much less than a Hubble time t ~...
(1) Incorrect, since the root mean square speed(c^2）is directly proportional to the temperature, but it will just affect the average kinetic energy, doubling the k.e., but not related to the potential energy.
(2) Correct, since the volume of gas is directly proportional to the temperature
(3)...
The answer given for part (c) in the back is that temperature doesn't change as the gas in cylinder A expands to fill cylinder B.
The thermodynamic system here is composed of the two cylinders A and B joined by some pipe.
But, I cannot find a satisfactory explanation for temperature...
The other day I read on a website that a lower evaporator airflow causes lower low pressure side saturation temperatures and higher delta T on an air-conditioner. Now I think I know why a lower evaporator airflow would cause a high delta T. If there is less air moving over the evaporator, the...
Hello,
My house has some heat loss. As an example I know the outside door temperature. How can I calculate the heat loss delta if I reduce the door temperature by 1 degree?
I know that there is a formula to calculate a heat loss based on the U-value of a fabric. But I can't get those values...
TL;DR Summary: Help needed with plotting heat maps, using data we gathered in an experiment.
Hello,
so I'm having problems with analysing data, which we gathered from an experiment we did in class. This is meant as a type of non-guided experiments class, where we are just given an initial...
I have a question about the temperature of HII gas. According to Table 1.3 in Draine's book (physics of the interstellar and intergalactic medium) this temperature is T~10^4 K.
I get a similar value by using the Saha equation for a hydrogen gas.
However, a naive estimate of the same temperature...
Hello,
I am stuck how to proceed with the equations below.
The problem:
A tank containing ##m_0## mass, with a temperature of ##T_0##, is to be filled with a total mass of ##m_1##, with the constant mass flow rate ##G## and temperature ##T_1## during ##t_p## seconds. ##T_0>T_1##. Other than the...
A diatomic molecule ##D_{2}## in ##30K##, in ##t=0##, is in the state ##| \psi (0) \rangle = \frac{1}{\sqrt{26}}(3 | 1,1 \rangle + 4| 7,3 \rangle + | 7,1 \rangle )##, where the kets denote states ##| l,m \rangle##. Use ##\frac{\hbar}{Ic4\pi}=30.4cm^{-1}##.
Obtain ##| \psi (t) \rangle ##
I...
I proceeded in the usual manner in which we take ##dU = 0## in the case of free expansion because there is no heat transfer in the box, as well as no work is done.
We can write, taking ## U ## as the function of ##V## and ##T##, $$ dU(V,T) = \left( \dfrac{\partial U}{\partial V} \right)_T ~...
It is 21°F here this morning and no frost on anything not even car windows. I have noticed this before when it gets cold enough there is no frost. Maybe all the moisture freezes out of the air and there is no moisture to make frost? I don't know? At what temperature is there no frost?
So the question goes like this: find change in internal energy in process 1->2 using diagram. And offered solutions a)-400J b)400J c)600J d)800J.
First I found T1 and T2 using (P*V)/T=R and got T1=24K and T2=72K. Then I found n(number of moles) using PV=nRT and got n1=1mol, n2=1mol. Then I...
Hello,
I am looking for assistance regarding temperature losses along a length of pipe with hot air entering one. I need to know the temperature leaving the other end of the pipe.
I have been able to calculate the W/m-K (in theory but stopped a i knew the answer wasnt what i needed) losses but...
Imagine, in a mercury ring (superconductivity below Tc=4.15 K) we establish a persistent supercurrent. Then we organize temperature cycles (T-cycles) in the cryostat, from 3 K to 2.5 K and back. According to the BCS theory of superconductivity, the pair density decreases at warming, i.e. a not...
Sir, heat is proportional to the vibration of atoms. If the vibration of atom is restricted to large extent due to intense gravitational field but has high quantity of total energy in the atom then does it mean it has high tempearture like the stars?
If you were to condense all the energy in the universe into a point, wouldn't the temperature be very high, yet the entropy be very low? Also if you were to spread out all of the energy in the universe, wouldn't the temperature be near zero and the entropy be very high? And this makes entropy...
I was watching a video about energy storage, and the subject was stuff that was around 1500° celsius, and for the whole video the graphics kept including Fahrenheit equivalents. Now I use Fahrenheit when checking the weather outside. But that doesn't make 2732F° any more relatable a...
Is the curie temperature of a ferromagnetic material constant? Are there any factors that will raise it or lower it? For instance, what happens if my piece of iron is already in a strong magnetic field? Is the curie temperate higher, then?
Hi,
I'm trying to solve a problem involving radiation in a triangular cavity:
As you can see, lengths and emissivities of all surfaces are given. For two of them, the heat flux is known and the temperature has to be found while for the remaining surface it's the other way around.
I have the...
A family member shared an article about thermovoltaics being developed at MIT with support from National Renewable Energy Lab (NREL).
A new heat engine with no moving parts is as efficient as a steam turbine
https://news.mit.edu/2022/thermal-heat-engine-0413
The article mentions that the...
I can’t quite work my head around this question, I am having a difficult time analyzing the question, I can’t seem to make out what the initial and final conditions are
would appreciate all the help I could get cheers
Hello there.
I have been conducting a thermal calculation of a fuel assembly for KLT-40S reactor (a small modular PWR-like reactor installed at the floating nuclear power plant "Akademik Lomonosov" with electric power of 35 MWe.) and obtained some interesting results. It seems that cladding...
The volume of the cylinder is ##V=\pi r^2 h=\frac{7\pi}{250}\ m^3## the number of moles is ##n=\frac{15}{16}\ mol## so from ##PV=nRT## we get ##P=\frac{nRT}{V}=25975.5\ Pa##.
Now, for the second question, it should be an isochoric process so ##V_2=V_1## and ##P_2=P_1+0.8P_1=\frac{9}{5}P_1## and...
Hello everybody. I would like to ask a question;
if I change the dimensions and densities and the material number identifier ZAID to a specific temperature.
Does MCNP change automatically the volume of the cells? or I have to change the volume of each cell manually and indicate it in the cell...
My first question here, so maybe not adequate or in the wrong topic, excuse me. I try to understand vibrating light harvesting antenna in biochemistry but it is a question of physics. We talk about a molecule with an emission spectra peak of about 650 nm.
In classical physics electrostatic and...
I know for sure PICO will be measuring polarization anisotropies with high fidelity. In addition, the PICO science paper shows that it will make full-sky Compton-y maps but the plots are mostly limited to l=1000. Will PICO be able to measure kSZ temperature anisotropy at l=3000?
If there weren't phase changes occurring I know that the temperature equilibrium would be ##T_e=\frac{m_{ice}c_{ice}T_{ice}+m_{w}c_{w}T_{w}}{m_{ice}c_{ice}+m_{w}c_{w}}##.
Now, by repeating the reasoning to get the above formula (##\sum \Delta Q=0##) and adding the phase changes of the water...