# All Questions

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### 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.
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 ...
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?
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 ...
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) ...
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 ...
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 ...
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?
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 ...
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 ...
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 ...
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 ...
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 ...
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 (...
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 ...
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 ...
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°...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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.
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 ...
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 ...
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 ...
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 u(\lambda,T)=\frac{f(\lambda T)}{\...
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 ...
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 ...
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 ...
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 ...
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 ...
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?
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 ...
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 $m$ ...
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 ...
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?
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 ...
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 ...
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 ...
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 ...
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?...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
### 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 ${\epsilon}_{j}=j{\epsilon}$ ...