Joule Definition and 82 Threads

$$\delta W_{rev}=-PdV\tag{3}$$ and so $$(dU)_{rev}=TdS-PdV\tag{4}$$ For an irreversible, closed system we have $$(dU)_{irrev}=\delta Q_{irrev}+\delta W_{irrev}\tag{5}$$ My question is about the following statement Sure, internal energy is a state function. I still don't understand...

Hi, Starting from dS in term of H and P, I'm trying to find ##(\frac{\partial H}{\partial P})_t## in term of ##P,V,T, \beta, \kappa, c_p##. Here what I did so far. ##ds = (\frac{\partial S}{\partial H})_p dH + (\frac{\partial S}{ \partial P})_H dP## ##ds = (\frac{\partial S}{\partial H})_p [...

Mentor's note: Moved from HW for a better fit Homework Statement:: A joule is defined as "the energy transferred to an object when a force of one Newton acts on that object in the direction of its motion through a distance of one meter." Explain this definition. Relevant Equations:: 1J = 1N.m...

Wikipedia says, Unlike a free expansion , in Joule Thomson expansion work is done causing the change in internal energy. Whether the internal energy increases or decreases is determined by whether work is done on or by the fluid; that is determined by the initial and final states of the...

Hi, I understand mathematically why using low resistance results in a greater heating effect. Could someone give an intuitive and microscopic picture of why the current contributes more to a greater power dissipation by the resistor rather than the resistance contribution to the power...

Hello all! First post here, and I apologize in advance if this question belongs elsewhere- I'll learn as I go. I am interested in knowing more about energy and performing work. In particular, if I have an object I would like to lift, how much energy I need to expend to do that. Take for...

I have solar radiation data in the units of Joule per cm^2 (joule per square centimeter) measured hourly. I want to use this data in evapotranspiratin calculation which requires radiation units as Watt per meter squared. How can I do this conversion?

Relevant Equations: Specific Work Done: w = \frac{p_2 v_2 - p_1 v_1}{1-\gamma} (1) w = \frac{R}{1-\gamma} \times (T_2 - T_1) (2) Thermal efficiency: \eta _{th} = 1- \frac{1}{r_p ^ {\frac{\gamma - 1}{\gamma}}} = \frac{w_{out} - w_{in}}{q_{in}} = \frac{q_{out} - q_{in}}{q_{in}} (3) Context...

example) E = 2734.2 joules per gram P = 2.73 x 109 watt/gram q: How can this conversion work? E = 21000 joules per gram P = ?

Homework Statement ##\mathbf A##.Joules heating Consider a metal in a uniform temperature in a static uniform electric field E.An electron experiences a collision, and then after a time t, a second collision. In the drude model , Energy is not conserved for collisions, for the mean speed of an...

I'm working on a small crank-able light using a DC motor,capacitors, and LEDs with a joule thief to drain the capacitors completely when the voltage in them drops too low for the LEDs. However I want the power from the capacitors to be able to go directly to the LEDs before the capacitors drop...

A double covalent bond of nitrogen (N2) is 15.58eV Now let's go into a example. if i have a laser that is 477nm and i do 1240/477nm then i get 2.6eV per photon. Now if i do (15.58eV / 2.6eV) it equals ~6 photons. Now to figure out how many Joules are required for 1 photon I do (6.626*10^-34S *...

Homework Statement Estimate the pressure increase required to impart one joule of mechanical work in reversibly compressing 1 mol of silver at room temperature. Same process for alumina. Homework Equations W=-PdV dV=V(alpha)dT-V(beta)dP dT=0 The Attempt at a Solution I used the work...

I'm trying to understand the Joule-Thomson effect in a more qualitative way. Here's my attempt at an explanation: Real gases experience intermolecular forces. If we expand a gas whose attractive interactions dominate, it'll cool down. This is due to the potential energy increasing and the...

Homework Statement 2. Homework Equations [/B] Consider the following circuit where: $$R_A=330 k\Omega$$ $$R_B=220 k\Omega$$ $$C= 2.2 nF $$ $$v_1(t)=6u(t) V$$ $$ i_2(t)=-10u(t-t_2) \mu A$$ $$t_2 = 12 ms $$ All the currents go clockwise (with the obvious exception of the current source)...

1. The problem statement, all variables and given/known d Hi have this problem but I don't know how to represent, however I've tried. The problem says: You are designing an electric grill and you have to choose a resistance circuit between the circuits shown the figure. Consider that every...

Hi Suppose there is a 1 m3 cylinder containing 1.3 kg air at 25 C. The cylinder is sitting in a vacuum place. The air inside the cylinder will exert a pressure of almost 1 atm. The cylinder also has a valve which can be opened to let the air out into surrounding vacuum. The average speed of...

Homework Statement For an engineering assessment (first year with no electrical background), we are using a solar panel to power an element for a distillation system. we have calculated our heat energy output requirement that we need from our heating element as being 800 J/s. For simplicity we...

Hi , How can I calculate the resistive heating occurring in the internal resistances of a solar cell ? Are ohm's law or the power dissipation relation P=RI2 applicable in this case ? if not the case how can we calculate the resistive heating there? Thank you in advance for your help

Say I have a line of steam with temperature 800 deg C, at 10bars connected with it is a partially evacuated tank 0.01 bar pressure, room temperature. The connection was built with a long capillary and a valve. Does throttling effect experience when the valve suddenly opened? Why and why not?

we all know the equation for KE 1/2mv^2 you do this simple math and you get an number that is in KE units , Joules. so, why is the KE unit equation, 1 Joule = Kg x (m^2/s^2) ?? 1Kg traveling at 1m/s would have a KE of 1Joule, but using the KE equation, it would be 1/2 a Joule. why is...

Work unit is said to be Joule and Energy unit is also Joule. Work formulas in F x S ( Force x Displacement) . We know 1 J = 1 F x `1 s Now Energy is also measured in Joule(J) So can we state : E = 1 F x 1 s as 1 J = 1 F x 1 s that is E = W Then why work and energy are different by definition...

I have a supercapcitor to power some of my small projects. The only problem is that the voltage drops gradually, unlike a lithium ion battery, in which the voltage is mostly stable throughout. My boost converter that I am using to boost the voltage up to 5 volts, stops working with an input...

I just came across Table 2 on pg 173 of...

Homework Statement I read about Joule's experiment proving the transformation of mechanical work into heat. But say I have a bowl with some water, and I start turning a spoon in it very fast, thus doing work - the water won't get hotter! What am I missing? Homework Equations conservation of...

I would like to make a pendulum go on moving by a permanent magnet that pushes the pendulum back with a force that is big enough to make it swing back with the same height. Can anyone tell me how much energy could be generated by a pendulum with height is 2 meter and 60 kg, swinging 90 degrees...

The Joule coefficient, μJ, is defined as μ = (∂T/∂V)U. Show that μJ CV = p – αT/κ Relevant equations Cv=(∂U/∂T)v κT=-1/V*(∂V/∂p)T α=1/V*(∂V/∂T)p dV(T,p)=(∂V/∂T)pdt+(∂V/∂p)TdpWhat I have attempted was to make μ = (∂T/∂V)U=(∂T/∂U)V(∂U/∂V)T=(∂U/∂V)T*Cv-1. Then α/κT=(∂V/∂T)p/(∂V/∂p)T because the...

Hi Is it possible to convert coulomb to joule without knowing volt?

Dear forum I am working with thermal radiation. This is the specific formula: P = σ ⋅ A ⋅ T4 P = emitted effect (W, J/s) σ = Stefan-Boltzmann constant (5,67 ⋅ 10-8) A = area of object (m2) T = temperature of object (K) How can I get to know the...

Good Day, I am looking for mathematical modelling of Joule heating of a simple cantilever beam . Can anybody provide me good source of relevant material. Thanks in advance.

Hi everyone..I'm trying to build a Joule Thief circuit operating on a 1.5V cell. Which transistor should I use? I have BC547 but I'm not sure it will work...Suggestions are welcome..

Hi everyone, I have to build a simple Joule thief circuit for school. Here it is :(http://upload.wikimedia.org/wikipedia/commons/8/83/Joule_thief.png). The resistance of the resistor is fixed to 1 kOhms, the voltage across the "dead battery" is about 1.5V, the transistor needs about 0.7V to...

Hi forum, First time poster. I'm in thermo this year and it's the first time working with pascals and joules. My teacher and most post just jump right into the equations, 1Pa = 1N/m^2 and 1J = 1N * M. But what really is a pascal? I get what a N is, force to move 1kg*m/s^2. If I convert N, I get...

Lets suppose we have 2000 kcal and we want to translate it joule. 1 calorie is 4,2 J/gC isn't it so I think it will be 8400000 g m^2/s^2 But my teacher says its 8400000 kg m^2/s^2 Which one is true Thanks

Homework Statement There's a person and he ate a hamburger which its 2000 kcal.And he wants to spend this energy . he will be weightlifting and he will lift 45 kg to 2 meters.How many times he can lift it ? Homework Equations W=Fx or W=mgh The Attempt at a Solution 2000...

Hello, I am a high school student carrying out a physics experiment. I created a short circuit in order to see how much heat different types of metals would release when a current is running through them (4.5 A). In my experiment, I tested three different types of metals: Brass, Stainless...

Ok so as fare as I understand the equation for Joule heating in a material with a DC current is I^2*R. I am trying to calculate for the heating of carbon fiber in an argon environment. Carbon fiber has a resistivity similar to graphite (roughly 5.0*10^-7) I am trying to calculate for 3.3VDc...

Homework Statement Using basic thermodynamic relations, show that the Joule Coefficient is given by: Homework Equations {\left(\partial T \over \partial V \right)_U}=-{T^2 \over C _v}{\partial \over \partial T} \left(P \over T \right)_V The Attempt at a Solution I started with the cyclic...

Homework Statement Hi, i have a little problem with a demostration, I hope you can help me. Homework Equations this said that we have a system, a gas is containing in a recipe, there's no heat exchange neither work with the enviroment, only an expansion v to 2v, we have to find that...

Hi all, some background info, thanks for reading and helping! I'm working on a project, the portable device is to vaporize glycerol(300 C). In an attempt to maximize vapor production, I've decided to skip the experimentation and calculate the optimal specs for each part. Also pardon my...

I read on 27 chapter from Blundell's Thermal Physics 2nd edition. For ideal gases, Joule expansion doesn't cool gases. But for real gases, Joule expansion makes cooling effects. And this book(page 314) says that when gases expand, their potential energy of molecular interactions...

Energy is E=γmc^2, but when I calculate this, will my result be in joules? I am unsure what the units are when I calculate it, and I keep hearing people saying joules. Also, what is PJ and MJ?

When my textbook talks about energy it starts with kinetic and potential. The derivation goes like this. F=ma=m(dv/dt)=-mg then they split the derivative using chain rule (dv/dt)=(dv/dy)(dy/dt) therefore since (dy/dt)=v we get F=mv(dv/dy)=-mg then they write mv dv= -mg dy...

Hello, I have the following problem: I would like, from a tungsten filament which an electric current is imposed, find the temperature emitted from the filament (Joule heating) on ansys workbench. I have to study a thermoelectrical , but I can not find any tutorial. Does anyone have...

Diesel, Otto , Joule TRICK? Hi Guys, I try to callculate the efficiency for a cycle Process. For Diesel, Otto and Joule Processes you can write the efficiency as a really small equation. I have seen that for example sometimes the adiabatic equation is used, but i don't understand in which...

In that experiment , the internal energy is zero , volume increase , pressure of system decrease, then temperature will constant ? Thanks

Assume we have an ideal gas of N particles inside a thermally isolated cylinder of volume V, and that the cylinder is equipped with a piston that can trap the air on one side. (Assume the piston occupies no volume in the cylinder.) Initially, the piston is fully withdrawn and the gas occupies a...

Is the equation JT = (1/Cp)(2a/RT - b) valid for adiabatic free expansion of real gases only? How was this equation derived?

Homework Statement This is the last part of the question. So far have been made to derive: ## \mu _{\text{JK}}=\left(\frac{\partial T}{\partial P}\right)_H=-\frac{1}{C_P}\left(\frac{\partial H}{\partial P}\right)_T ## Then ##\left(\frac{\partial H}{\partial P}\right)_T=V - T...

It's amazing that a name like that can grab the attention of so many people and trigger such a flurry of constructing. Is looks to me as if it's a way of driving a non linear device like an LED is such a way that it produces more light output than it would from a battery. Is it not just...