All Questions

Filter by
Sorted by
Tagged with
0
votes
0answers
119 views

What would theoretically lead to a greater burn if both materials are kept at a constant temperature when applied to the skin? Water or Brass? [closed]

This is a question that would help with the understanding of specific heat and conductivity and which has a greater effect when it comes to transfer of energy between objects.
0
votes
1answer
42 views

Deriving Planck's Constant from Wien's Displacement Law

So I'm reading an introductory book on Quantum Theory (David Park, 3rd ed.) and I am having trouble with the following question: "According to Wien's displacement law, the wavelength $\lambda_m$ at ...
-2
votes
2answers
51 views

Can Entropy Change be negative in this situation?

The temperature of two moles of an ideal diatomic gas is decreased from 𝟔𝟎𝟎 𝐊 to 𝟑𝟎𝟎 𝐊 at constant pressure. Is entropy change negative?
0
votes
2answers
90 views

Which is positive? which is negative? about laws thermodynamics…from problem solve

1) A hot block of iron does 50 kJ of work on a cold floor. The block of iron also transfers 20 kJ of heat energy to the air. Calculate the change in energy (in kJ) of the iron block. 2) A chef ...
0
votes
1answer
23 views

How much energy from air to ice? [closed]

If... "A" is the mass of air (standard air composition and pressure) "I" is the mass of ice "V" is the volume of the box where the change of heat happens (no heat interaction with out of the box) ...
-1
votes
2answers
90 views

How many calories of energy does it take to heat up 1 cubic inch of water 1 degree Fahrenheit? [closed]

In metric, one milliliter of water occupies one cubic centimeter, weighs one gram, and requires one calorie of energy to heat up by one degree centigrade--which is 1 percent of the difference between ...
1
vote
1answer
56 views

Temperature distribution with advection problem

A very long pipe enters an oven at $x_1$, with oven temperature set to $T_{\infty}$. Fluid flows through the pipe at mass flow $\dot{m}$ (flow speed is $v$), initially at temperature $T_0$. Flowspeed ...
0
votes
1answer
40 views

Relation between Temperature and heat current

This problem: I was able to solve it doing this: But I think i have nowhere " exploited " the equivalence given above. How can this be used in this problem?
0
votes
1answer
43 views

Calculate temperature decrease of an evaporating droplet

I have a small droplet of Cyclohexane which evaporates at room temperature and ambient pressure. I measured the volume at two different times ($\Delta V=1.5\times10^{-10}$ m$^3$). I would like to ...
0
votes
0answers
27 views

Calculating rate of change of thermal energy and applying that to usage in calculating the time it takes to reach equilibrium

So if I have an experiment with two gases that are identical and have a specific heat of 100 j/(KM) and there is a divider in between the gases with a surface area of 1 square meter, and a thickness ...
0
votes
2answers
226 views

Finding temperature at junction of rods

Let's say I have three tubs, from left to right Tub 1, Tub 2, Tub 3. Tubs 1 and 3 are at 50 degrees Celsius and Tub 2 is at 10 degrees Celsius. Tubs 1 and 2 are connected by a copper rod, and tubs 2 ...
0
votes
1answer
80 views

Proving that $c_V$ is positive

On my professor's lecture notes he claims that $c_V>0$. Intuitively, this would have been my guess as well but he mentions how you can prove this by constructing a setup: "Construct an isolated ...
0
votes
1answer
57 views

Calculating temperature of objects after colliding

So, I'm making a physics engine, and I need to know what is the temperature object A has after colliding with object B. Object A is 10 earths in diameter, and is 10 earths in mass. Object B is 5 ...
0
votes
1answer
68 views

Specific heat of water in unit J/kg °F

We know that specific heat of water is 4186 J/kg °C This is the amount of heat per unit mass required to raise/change the temperature by one degree Celsius. We also know that ∆°C = 5/9 °∆F = ∆K (...
1
vote
1answer
184 views

Derivation of Helmholtz free energy and associated relation

I am quite new in thermodynamics and I have never touched it so far. But now I have some basic questions that I hope someone can kindly explain them to me. I know the Helmholtz free energy is ...
0
votes
1answer
71 views

Entropy generated for a warm bath heating a cold rock

Put a cold rock of heat capacity $C_r$ and temperature $T_{r1}$ into an insulated fluid bath of finite heat capacity $C_b$ (the bath is not a reservoir) and temperature $T_{b1}$. Now let the entire ...
0
votes
1answer
76 views

Is rate of heat loss constant or does it vary? [closed]

Suppose a body cools from 70°C to 60°C and then again cools from 60°C to 50°C. If surrounding temperature is 30°C then the rate of heat loss from 70° to 60°C would be different to that from 60° to 50°...
0
votes
2answers
103 views

Given $2\text{ °C}$ atmospheric temperature rise, what would be the temperature increase if confined to an oven?

Consider the 2 °C average global atmospheric temperature rise as discussed by the IPCC. Assume an oven with an the interior that is a perfect cube having a volume of one cubic meter, empty of ...
0
votes
1answer
23 views

Wind direction affecting temperature,

I am working on a paper for a Graduate School class and I wonder how can I create an experiment that shows how wind direction affects temperatures? I understand the concept myself however I want to ...
-1
votes
1answer
447 views

Final temperature of ice and water [closed]

My answer doesn't seem likely but I can't see where I've gone wrong: Q: Ice of mass 0.125kg at -5 degrees is added to water of mass 0.25kg at 8 degrees. Calculate the final temperature of the water ...
1
vote
1answer
143 views

Determine temperature from Sound?

I was told that you could determine the air temperature by using a BoomWhacker (its a muscial instrument that is a plastic tube and when you strike it against a surface, it will produce one and only ...
-1
votes
2answers
465 views

Calculating surface temperature from solar radiation? [closed]

Knowing how much solar radiation an object is exposed to, how can we calculate the temperature on the surface of the object? Example: If we have $800 \frac{W}{m^{2}}$ incoming solar energy onto a ...
0
votes
2answers
825 views

Heat capacity increases with temperature

This is a problem I came across: Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at 100 ºC, while the other one is at 0 ºC. If the ...
-3
votes
1answer
144 views

Temperature of 100w bulb [duplicate]

What is the running temperature of a 100w bulb if it's resistance while on is 50 ohms and the mains voltage is 240 V RMS.
-2
votes
1answer
308 views

Temperature coefficient of resistivity

I came across a question recently: A wire has a resistance of 2.1 ohm at 300 K, and 2.7 ohm at 373 K. What is the temperature coefficient of resistance of the metal? I tried by simply putting ...
0
votes
1answer
35 views

Find ordinary differential equation which discribes the situation of heating up a building

First of all I would like to emphesize that I am not a physicist, our professor gave us this exercise to train our ability of making differential equations. Since it is related to physics only, I ...
1
vote
2answers
279 views

Calculating temperature of insulated container over time

Experiment In Science Olympiad there is this competition called Thermodynamics. In thermodynamics, we have to make an insulating box that is smaller than 15cm by 15cm by 15cm. This box will have a ...
0
votes
1answer
335 views

Derivation of Wien's displacement law

I know this might be a silly question, but is it necessary to know Planck's Law in order to show that $\lambda_{max}\propto\frac{1}{T}$? If you set \begin{equation} u(\lambda,T)=\frac{f(\lambda T)}{\...
-3
votes
1answer
55 views

I have a question about Temperature and materials. Can anyone help please? [closed]

Let's say you have a slab of material of thickness (x) and one side is exposed to a temperature. I need an equation that represents what the temperature will be on the other side of the slab. I assume ...
0
votes
2answers
114 views

What calorimetry approach is this?

Question: Find the final tempertature of the system when $5gm$ of steam at $100^\circ C$ is mized with $31.5gm$ ice at $-20^\circ C$. Constants: Specific heat of ice and specific heat of steam is ...
-1
votes
2answers
50 views

What is the equation relating the mass of water and its temperature change in a fixed time?

I heated up a beaker of water to 70˚C and set a time of 2 minutes. I measured the change in temperature in that time interval. I changed the mass of water and measured the change in temperature each ...
1
vote
1answer
86 views

How to estimating the heating cost of an open bathroom window?

I forgot to close the bathroom window in the morning and the heating was on. I'm wondering if it's possible to roughly estimate the costs? Unfortuantely I have not much physics knowledge. I just ...
-1
votes
1answer
550 views

heat capacity of a hot metal in cold water [closed]

I've a hot pice of metal (temperature is $T_1$ Kelvin) and I put that in water (of temperature $T_2$ Kelvin), I also know the volume of the water $m_1$ liters. Then I put the hot metal in the cold ...
-4
votes
1answer
301 views

Analyzing the rates of cooling points using the graph and data [closed]

how should i use this data to analyse the differences between the two materials. and what calculations could i use for it?
0
votes
2answers
131 views

How much energy needed to liquify H?

I want to know how much pounds (or the correct measure) would an air compressor need to liquify Hydrogen As its boiling point is somewhat close to -250°C i want to know how to calculate the pressure ...
-1
votes
1answer
189 views

How do I convert natural/Planck units to SI? [closed]

I am looking at a paper which has set: $\beta=1/kT=1$ where k is the Boltzman constant. It uses natural planck units ie $m=\hbar=k=1$. Does it make sense to extract a temperature $T$ and mass $m$ ...
0
votes
2answers
50 views

Need help on the electrical resistances of semiconductors and metals and their dependance on temperature

So I was doing some problems and this came up : - Two resistors $A$ and $B$ having resistances $R_1$ and $R_2$ respectively at $0^{\circ}C$ and temperature coefficients $α_1$ and $α_2$ are joined ...
1
vote
0answers
45 views

Temperature of R-N Black Hole by Euclideanising the Metric [closed]

How to derive the temperature of the Reissner–Nordstrom black hole by euclideanising the metric?
0
votes
1answer
159 views

Temperature of a sphere heating up in the sun (average emissivity of the sphere unknown)

I'm stuck at the following exercise: Imagine an aluminum sphere that is painted matte white with an emissivity of $\epsilon=0.10$ at visible wavelengths and $\epsilon=0.95$ at wavelengths ...
1
vote
1answer
137 views

What would be the temperature of the resultant mixture?

The question in my textbook reads 100 g of water is supercooled to -$10^\circ$C. At this point, due to some disturbance mechanised or otherwise some of it suddenly freezes to ice. What will be the ...
1
vote
0answers
29 views

Is a high speed or low speed water droplet colder when it hits the floor? [closed]

I have two water droplets, about 2mm across, one with an initial velocity of $4ms^{-1}$ towards the ground, which is 5 metres away. The other has an initial velocity of $0ms^{-1}$. Both have an ...
1
vote
2answers
117 views

Hottest tea during your breakfast problem [duplicate]

Suppose you are having breakfast and you like to drink your tea with 50% milk, 50% tea. You like to drink your tea as hot as possible, but your friend already filled your cup with tea, so it's already ...
0
votes
2answers
309 views

Three parallel plates, approximated as black bodies

Consider three parallel plates, which can be approximated as ideal black bodies. If the left plane is kept at temperature $T$, and the rightmost one at $2T$, what is the temperature of the middle one?...
39
votes
10answers
8k views

Condensation of Water. Classroom Controversy

In our test there was a question that went like so: Question 4 You have a glass of iced water on an unshaded picnic table and went for a walk for 30 minutes. When you return you noticed the glass ...
0
votes
1answer
29 views

How to construct a more efficient cooler made by cheap materials to cool a glass bottle containing hot water without pouring the water out?

details -limitations:it can only use five blocks of ice and the cooler must consist one container to put the glass bottle.Also,cannot interfere the water in the glass bottle such as to stir it. but ...
0
votes
2answers
3k views

Resistance of fuse wire? [closed]

Qs. Fuse wires have ______________ melting point and ______________ resistance. Fill in the blanks with high and low. ----> Well according to me the melting point part is obvious. It will be low ...
-1
votes
1answer
67 views

No temperature change during diabatic expansion? [closed]

So, checking some exercises from previous exams of where i study at, there is an exercise that goes like this (copying only the relevant stuff): A mole of a diatomic ideal gas expands from A to B ...
0
votes
1answer
104 views

In terms of heat, temperature and the first law of thermodynamics: Is defrosting an energy saver

If I were to defrost my freezer would I save energy? From what I have read I would expect the answer to this question to be no, however it would be great to hear if Im wrong. I say it wouldn't save ...
1
vote
1answer
386 views

How can I find the final temperature of this mixture of two nitrogen tanks?

I have this question: You have two insulated nitrogen tanks. The first tank is at a pressure $P$ with a volume $V$ and at the temperature $T$. The second tank is at a pressure of 2P with a volume ...
0
votes
1answer
126 views

Find the probability that a system has energy $\epsilon$ at $T = \infty$

A system of $8$ identical distinguishable particles is in equilibrium in a heat bath at temperature $T$ Each particle has $5$ states with equally spaced energy levels ${\epsilon}_{j}=j{\epsilon}$ ...