Internal energy Definition and 369 Threads

In magneto caloric effect, we see that when a substance in an adiabetic closure is exposed to external magnetic field, its temperature increases. But the internal energy of the substance has to be constant so this implies decrease in internal potential energy. However the application of magnetic...

Homework Statement Show that the change in internal energy of a simple system between states (V1, T1) and (V2, T2) is given by ∆U = \int^{T1}_{T2} C_v\ dT + \int^{V1}_{V2} T.\frac{\partial p}{\partial T}|_V - p \ dVHomework Equations dU=dQ-pdVThe Attempt at a Solution As U is a function of...

Hi there. Here is the deal, today morning in my thermodynamic class we were making some exercises of stability, and then surged a question about internal energy. The thing is I thought that the internal energy should be always positive in sign. This doesn't mean that the variation must be...

Homework Statement Why is this false? "if systems A and B each consist of pure liquid water at 1 bar pressure and if TA>TB, then the internal energy of system A must be greater than that of B" Homework Equations The Attempt at a Solution It seems true to me. Could it be that B...

Homework Statement A NON-monatomic gas expands from I to F in the Figure (Since it is not monatomic U=3/2nRT does not give you the internal energy, this only works for monatomic gases, instead you must use the first law). The energy added to the gas by heat is 424 J when the gas goes from I to...

Homework Statement Assume ideal gas conditions. Cp=(7/2)R, Cv=(5/2)R 15 moles of airis contained in a cylinder and prevented from escaping by a frictionless piston initial conditions are 1.5 bar, gas volume 0.2m^3 final conditions required are 10 bar t 27 degrees celsius calculate...

If we melt ice at 0'C to water at 0C, what is the change in the internal energy of the ice-water system? As per the first law of thermodynamics, ΔU = ΔQ +ΔW where they are increase in internal energy, heat flow to the system and work done on the system respectively. If we melt ice at 0C, we...

In thermodynamics Change in Internal Energy = Heat - Work (\DeltaU=Q-W) During vaporization my Heat is mass*Latent Heat (Q=mL) and Work is Pressure*change in volume (W=P\DeltaV), so \DeltaU=mL-P\DeltaV. Let's take any of the natural monoatomic gases, Neon in this case. \Delta = Volume...

As a practical matter, the internal energy of a system is treated as a state function of a the system and is concerned only with the kinetic energy of particles, not the potential energy. So for thermodynamic entropy, S=E/T, (S=entropy, T= absolute temperature) I'm considering E to be kinetic...

Homework Statement A helium balloon with a volume of 1m^3 and temperature of 27 deg c is placed in liquid nitrogen in an open container and cools to a temperature of 77 K. Assume that helium behaves like an ideal gas at constant atmospheric pressure and find the new volume of the gas in the...

Homework Statement A container of volume 0.72 m^3 contains 1.4 mol of argon gas at 24 degrees C. Assuming argon behaves as an ideal gas, find the total internal energy of this gas. The value of gas constant is 8.31451 J/mol x K. Answer in units of J. Homework Equations PV=nRT...

How to calculate Energy absobed by the components of a Truck Cab after crash test?? Hi, I have a question regarding the calculation of internal energy of components after collision. In conducting the frontal impact test as per the ECE R29 regulation, a swing bob has to hit the front of...

Homework Statement Helium (He), a monatomic gas, fills a 0.010-m^3 container. The pressure of the gas is 6.2 multiplied by 10^5 Pa. How long would a 0.38-hp engine have to run (1 hp = 746 W) to produce an amount of energy equal to the internal energy of this gas? Homework Equations...

We known U=3/2nRT (monatomic ideal gas), just depends on temperature. Most texts assert connecting U and Q with constant volume condition and say"\Delta U = nCv\Delta T for any process because of internal energy only depends on temp". I think that statement is very strange. Deriving...

Homework Statement Two grams of water are sealed in a rigid con- tainer; then the water is vaporized by heating. 1664 cal of heat is needed for vaporization. What is the change in internal energy of the water? Answer in units of J. Homework Equations 1 kcal= 4,186 J The Attempt...

hi, Can anybody explain the phenomenon behind internal energy? and what is the change in internal energy when water evaporates. Please do give reference to first law of thermodynamics. Thanks in advance.

Homework Statement Show that internal energy U = U(T) only for an ideal gas who'se equation of state is: P(V-b) = RT (the claussius equation for n moles of gas) Homework Equations Thermodynamic Equation of state: \left(\frac{\partial U}{\partial V}\right)_T =...

Why is internal energy not sufficient to compare states? Thank you for your answer.

Is the internal energy for a closed cycle always zero?

Hi, 1. \color{blue}dq=dU+PdV so C_V = \left(\frac {\partial q}{\partial T}\right)_V= \left(\frac {\partial U}{\partial T}\right)_V leads to dU=C_{V}dT so \color{red}\left(\frac {\partial U}{\partial V}\right)_T = 0 meaning that internal energy of NONideal gas is a sole function of T? 2. As...

Homework Statement Water at the top of Niagara Falls has a temperature of 10.0degrees celsius. If it falls a distance of 50.0m and all of its potential energy goes into heating the water, calculate the temperature of the water at the bottom of the falls. Homework Equations W = change...

Consider the following situation. Two particles are initially separated by some distance and are then pulled further apart, thus increasing the potential energy of the system (due to the gravitational force of attraction between them). If I am correct in understanding special relativity, then...

http://img689.imageshack.us/img689/511/pistonquerstion.jpg This is my part attempt... [PLAIN][PLAIN]http://img830.imageshack.us/img830/7342/internalenergyanswer.jpg And ideas on how I can do the rest of it?

Hello! First post here :-) Hope this isn't too simple for this forum...if so, by all means give me a pointer... I'm wondering about some basic thermod. concepts. Could somebody please shed a little light on these? Internal Energy and Enthalpy (both from macroscopic viewpoint) Does...

Can you help me with this problem? An ideal gas is compressed adiabatically. The work done over it is 200 J. How much will the internal energy change? A) 200 J B) 100 J C) -200 J D) 0 J Which formula do you use to solve it? Thanks in advance!

1. A gas bottle with a volume of 0.1 m3 contains 0.4 kg of a gas at a pressure of 7 MN/m2 and a temperature of 150 ºC. For this gas Cp = 10.54 kJ/kg K. Calculate the changes in internal energy when temperature is raised to 500K Given answer: 362 kJ 2. pV=mRT pv=RT...

Just had a thermodynamics exam, and one of the questions was For an ideal gas, is the relation \DeltaU = mC_{}v\DeltaT restricted to constant volume processes only? Why? I wrote that it was only valid for constant volume processes, because this is what C_{}V is defined as, however now I'm...

I'm working from Feynman's definition of internal energy for the Debye theory of heat capacity. I'm trying to use that to derive the normal definition of heat capacity that I've seen. But I'm running into a problem. Note, in the following V_0 is frequency, whereas V is volume (that's how Feynman...

What's the difference between enthalpy and internal energy? Internal energy is the average of the kinetic energy (linear and angular) of the particles of the body (or system), right? Could someone explain me this clearly? Thank you

Homework Statement A 15.0 kg block is sliding across the floor. Initially, it is moving at 1.2 m/s. However, after sliding 20.0 meters, =7.5 J of work are done on it by friction. What is the block's velocity after sliding 20.0 meters? Homework Equations KE=.5v2 lw-l=F\DeltaXcos\theta...

What must be true for two objects of the same material to have the same internal energies? (Choose all that apply) a. The masses of both objects must be equal b. Both objects must have the same density c. The temperatures of both objects must be equal d. Separate objects cannot have...

Homework Statement I have two identical volumes of gas, and I heat them both to 100 C, one under constant pressure, one under constant volume. Which has more internal energy after the process? The attempt at a solution I believe that they both have the same as the extra heat you have...

Homework Statement A car of mass 2200 kg collides with a truck of mass 4500 kg, and just after the collision the car and truck slide along, stuck together, with no rotation. The car's velocity just before the collision was < 35, 0, 0 > m/s, and the truck's velocity just before the collision...

Homework Statement 2 moles of a monatomic ideal gas expands from state A to state B. PA = PB = 600 N/m2, VA = 3.0 m3 and VB = 9.0 m3. i. Calculate the work done by the gas as it expands. ii. Calculate the change in internal energy of the gas as it expands. iii. Calculate the heat added to or...

U is internal energy, which is the sum of heat + work done. \DeltaU = q + w -----(1) where w = \Delta(PV) Enthalpy is the internal energy + work done \DeltaH = \DeltaU + P\DeltaV At constant pressure, \DeltaH = q - P\DeltaV + P\DeltaV \DeltaH = q_{p} Where q_{p} is used to...

In my book it says that the change in internal energy = Q -W Yet, my teacher says that its Q + W He says that it's reversible due to the signs... but i don't know what that means... can somebody give me an example?

Hi there, I have some serious problems with a couple of questions. Need help for exam revision. 1.1 Homework Statement A 2kg chunck of ice at -10Celsius is added to 5kg of water at 45Celsius. What is the final temperature of the system? 1.2 Relevant equations specific heat capacity of ice -...

Homework Statement Suppose 1 g of water vaporizes isobarically at atmosphere pressure (1.013 x 105 Pa). Its volume in the liquid state is Vi = 1 cm3, and its volume in the vapor state is Vf = 1671 cm3. Find the change in internal energyHomework Equations \Delta U = \Delta Q - \Delta W \Delta...

Homework Statement Please help with this problem! How many sprints from rest to a speed of 4.5 m/s would a 59 kg woman have to complete in order to burn off 5.0 x 102 Calories? (Assume 100% efficiency in converting food energy to mechanical energy.) Homework Equations...

hello happy new year i'm a little confused here after i saw this U= KE + PE + H(enthalpy)----------------------1 while it is known that H=U+PV------------------2 i'm sure that eqn 2 is true but do you think with m that 1 is not true ?? the problem is that my instructor use...

Homework Statement The internal energy of a system increases by 200 J while 900 J of work are performed on it. What was the magnitude of the heat flow into or out of the system? Does the heat flow "out of" or "into" the system? Homework Equations Don't really need. The Attempt...

In polytropic process internal energy change is=mCv(T2-T1)? why is it not mCp(T2-T1)? Why are we not taking specific heat at constant pressure?

\Delta U = Q - W = Q - PV (where PV is the work done BY the system). \Delta H = \Delta U + PV (where PV is work done BY the system). 1) Above I defined PV in both equations as work done BY the system. I think this must be correct to show that when P is constant we can have \Delta H = Q...

If we apply 300 kJ of heat to 2500 moles of air at constant pressure, what is the change in internal energy? So far i think I use the equation: (f/x)nkT, but I don't know how to calculate the degrees of freedom and whether I do or not, and whether or not to calculate the number of moles by...

Hi, This is not exactly homework, but I'm not sure it belongs in any other section either. I've been reading through Applied Thermodynamics for Engineering Technologists by Eastop & McConkey. In general it's pretty good I think. However, in the first few chapters, it explained that Q+W =...

internal energy of a gas :( Hi all! I have a problem with this equation ΔU=mCvΔT, where ΔU=change in internal energy, m=mass, Cv=specific heat of air/gas at constant volume,ΔT=change in temp. Although this expression is true for all processes which can be applied to a gas e.g polytropic...

Homework Statement One mole of an ideal diatomic gas undergoes a transition from. a to c along the diagonal path What is the change in internal energy? Homework Equations The Attempt at a Solution I've tried to use the two other paths since the internal energy is the same both...

I know that phase changes, such as the melting of ice, occur at constant temperature. Doesn't this imply that the change in internal energy during the phase change is zero, since the temperature remains the same? I thought that in all isothermal processes this was the case, so that the First Law...

A steam engine of 1kg pulls 8 cars of 1kg each. The velocity of the engine is 0m/s initially then gets up to 4m/s in a time of 4 s while moving a distance of 5.3 meters. During that time, the engine takes in 134J of heat. What is the change in internal energy? Ok so i know that: internal...

Homework Statement The internal energy of a monoatomic ideal gas such as neon is simply the total kinetic energy of all its atoms. What is the internal energy of 2 liters of neon at a temperature of 200 K and pressure of 0.7 atm? Homework Equations PV = nRT KE(ave) = 3/2kT U =...