What is Joule: Definition and 81 Discussions

The joule ( jowl, jool; symbol: J) is a derived unit of energy in the International System of Units. It is equal to the energy transferred to (or work done on) an object when a force of one newton acts on that object in the direction of the force's motion through a distance of one metre (1 newton metre or N⋅m). It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889).

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  1. A

    Control Of Joule Heating Effect In Tungsten Wire.

    How can I accurately control the Joule Heating effect of a length of Tungsten wire to certain temperature ranges? The tolerance would have to be no more than a maximum of +/- 2°C. Would I require alternating or direct current and/or any other associated instrumentation? I have little or...
  2. P

    Finding the volume of a cube with 1 Joule

    Homework Statement Interstellar space, far from any stars, is filled with a very low density of hydrogen atoms (H, not ). The number density is about and the temperature is about 3 K. What is the edge length L of an LxLxL cube of gas with 1.0 J of thermal energy? I found: P =...
  3. D

    Joule Watt second = How many Plank?

    I hope someone can help me find quantity of electricity. how big is a Planck? In other words, how many Plancks per one second (unit time) equal one Watt-second (unit energy) at 60 hz (377 radian)?
  4. P

    Unit Joule is the unit of work and of kynetic energy

    Homework Statement That is what I learnt, and that it is expressed in Newton*meter. Then I learned that G is equal to 6.47 x 10^ -11 joules and that h is equal to 6.6262 x 10^ -34 joules x sec (N*m*s)and that one photon of light (say red) is equal to 4x 10^ 14 Hz(frequency) and its...
  5. B

    Is the Joule-Kelvin Expansion Reversible?

    Homework Statement Is the Joule Kelvin expansion reversible or not? Homework Equations The Attempt at a Solution It\'s definitely quasistatic but I\'m not sure if it is reversible or not? I have a feeling it\'s not but can;t explain why...any ideas?
  6. P

    How does Joule's Law explain gas temperature change?

    Hi :smile: I was reading about this experiment done by Joule that consists of: Some gas was kept in container A. Container A and B were interconnected. He allowed the gas from container A to diffuse, hence, occupying the container B as well. The system was well thermally insulated...
  7. C

    Joule kelvin expansion, thermodynamics

    Homework Statement for a jk expansion, I know dU=0. I think this is because dQ=0 as its isolated and dW = 0 as there is no work done against the surroundings. but is dW 0? does the gas do work against itself? I have also seen that the temperature change of an ideal gas = 0. how can...
  8. A

    Why does high voltage transmission reduce Joule losses?

    I'm a bit confused about why power is transmitted at high voltage for transmission over long distances. This is generally explained as reducing Joule losses, P = I^2 R, and we minimize the current by maximizing the voltage. However, a trivial re-arrangement using Ohm's law gives also P = V^2...
  9. B

    How Efficient Is a Solar Panel at Converting Sunlight to Electricity?

    Homework Statement A solar panel (an assemblage of solar cells) measures 58 cm x 53 cm. When facing the sun, this panel generates 2.7A at 14V. Sunlight delivers an energy of 1.0 x 10^3 W/m^2 to an area facing it. What is the efficiency of this panel, that is, what fraction of the energy in...
  10. B

    Compute Joule Heat in Heating Coils

    Homework Statement Two heating coils have resistances 12.0 ohms and 6.0 ohms, respectively. a)What is the Joule heat generated in each if they are connected in parallel to a source of emf of 115V? b) What if they are connected in series.Homework Equations Am I doing this question properly? The...
  11. B

    Energy in Circuits: The power lost to joule heating.

    Homework Statement The aluminum cable of a high-voltage transmission line carries a current 600A. The cable is 60km long, and it has a diameter of 2.5 cm. What is the power lost to Joule heating in this cable? Homework Equations Should I use the equation V=1/(4piEo)integral(dq/r) to...
  12. C

    What is a Joule Second? - Explained Easily!

    I can easily picture joules per second (I just see light of varying intensities passing a point at varying rates) I don't know what a joule second is. I know that Plancks constant is just to use the frequency of the photon to find out its energy but what in the name of God is a joule second?
  13. N

    Wikipedia's defintion of the joule is confusing me

    According to Wikipedia, a joule is "the energy exerted by the force of one Newton acting to move an object through a distance of one metre." That sounds like a joule is very inconsistent. We could apply one Newton to a bowling ball to make it move one meter, and we could apply one Newton to a...
  14. A

    Turboexpanfer joule thomson

    good morning you need not give a lot of details, basically right or wrong, sometimes a little explanation would be nice: 1. in a turbo-expander (used in rotating equipment to produce refrigeration temperatures at its gas exist), the turbine section is said to have free flow--what is free...
  15. J

    Joule Thomson Effect: Exploring the Minor Difference

    It occurs when a real gas is allowed to expand adiabatically we all know when a ideal gas is expanded adiabatically it temperature decreases so real gas should do the same with minor difference so what is all the fuss about we all know it will happen why is it given a special name
  16. S

    Modelling helium in the joule kelvin expansion

    How is it best to model Helium gas, Ideal gas equation? Dieterici? Van der Waals? some other equation? Also if it is dieterici or van der waals,what the values of a and b, the constants in the equation of state.
  17. C

    Joule Heating & Resistor Temp Increase

    I want to find the increase in the temperature of a resistor due to joule heating. I mean that if we apply some electrical power to a resistor then the electrical energy is converted to heat energy due to joule heating. The heat energy will increase the temperature of the resistor. Is it...
  18. B

    Searching for Joule Thomson and Thermal Expansion Coefficients of Methane

    I've been scouring the web in search of a Joule Thomson coefficient value for methane, but so far no luck. I have the volume, temperature, and specific heat as well... so I could also use the coefficient of thermal expansion for methane.. but I can't find that anywhere either! Does anyone...
  19. I

    Joule Mobile Mass Transporter Project

    Objective: To build a device that will transport a 1 kilogram mass a distance of 10 meters using the energy released as the mass falls a distance 10 centimeters. Rules: 1. The only source of energy that may be used to move the vehicle is a 1 kg mass falling 10 cm. 2. All parts of the vehicle...
  20. M

    Understanding the Joule: Defining and Applying Energy in Physics

    This is really basic, but I can't seem to find that one piece of reasoning that I must be missing... I don't understand the definition of the joule; 'the energy given to a body if a force of 1N is applied for the distance of one meter' If I apply 1N to an object of mass 1000kg until it has...
  21. S

    What Is the Joule Thompson Effect and How Is It Calculated for Different Gases?

    Hey all, I'm not sure this is a homework problem, more a problem I'm having with equations and this effect. Experimentally we measured dT and dp, I plotted them, then determined the Joule Thompson coefficients for 3 gases (He, CO2, N2). These values came out to be μJT(CO2) = .815 bar/K...
  22. J

    Efficiency of an engine performing the Joule ideal-gas cycle.

    Homework Statement The figure represents a simplified PV diagram of the Joule ideal-gas cycle. All processes are quasi-static, and C_P is constant. Prove that the thermal efficiency of an engine performing this cycle is 1 - \left(\frac{P_1}{P_2}\right)^\frac{\gamma - 1}{\gamma}...
  23. R

    Joule Heating, Calculating Filament Resistance

    The experiment is joule heating and I'm trying to calculate the filament resistance.1.) mass of the calorimeter cup 49.5g specific heat of the aluminum cup: 0.22 cal/kg*K mass of calorimeter cup w/ water 232.5g initial water temp. 20.5 C voltage across heater 7.3V current through heater 5A final...
  24. ~christina~

    Solving Joule Machine Problem [SOLVED] joule machine

    [SOLVED] joule machine.. Homework Statement In joule's apparatus below, the mass of each block is 1.50kg, and the insulated tank is filled with 200g of water. What is the increase in the emperature of he water after the bocks fall through a distance of 3.00m...
  25. C

    Deriving Joule-Thomson Effect: CNGA Approximation

    Hello ALL, I am looking for the derivation of joule thompson effect to show that Uj = (nBTave^-n / Roh(ave) Cp) *Zave where n = 3.825, B = 5287.Pave.10^1.785G Pave in KPa(g) and Tave in K using CNGA approximation. Can anybody help me in this? Thanks Shabbir
  26. X

    How Can I Maximize Efficiency in a 1 Joule Vehicle Project?

    Alright. I have a physics project due in about 10 days and I am not quite sure how to go about it. I have to make a "vehicle" move as efficiently as possible. I can only use 1 Joule of potentional gravitational energy per the equation mgh. The only specifications of the vehicle are that it is...
  27. S

    Constructing a Joule Car: Utilizing Gravitational Potential Energy

    Hey guys, I am involved in a competition where my objective is to build a Joule Car: Can anyone please give me ideas of how I can use gravitational potential energy to build it? Here are the actual directions: http://www.mrmaloney.com/nssl/events/2007-2008/0708_3-dec-joule-car.pdf Your help...
  28. T

    What is the Definition of 1 Joule and How Does it Relate to Lifting Objects?

    Someone told me that 1 Joule is roughly the amount of energy required to lift a 1 kilo object 10 cm of the ground. This sounds weird to me. Seems the amount of energy required would depend on how fast you lifted the object? The more time you were to spend lifting, the more energy you would spend...
  29. A

    How Is the Joule-Thomson Coefficient Calculated Without Knowing Volume?

    Hi. I need a little help with this question. I found a useful link below but can't figure out how to find the joule-thomson coefficient without knowing volume. I'd appreciate any pointers on this. Thanks. http://www.ccr.buffalo.edu/etomica/app/modules/sites/JouleThomson/Background3.html...
  30. S

    What Should Hl Be in a Joule-Kelvin Helium Liquefier?

    We have a helium liquefier which takes compressed He gas at 14 K, liquefies a fraction alpha and rejects the rest at 14K and atmospheric pressure. I've got to the stage alpha = (Hf - Hi)/(Hf - Hl) where Hf, Hi, Hl are the final, initial and liquid enthalpies respectively. I know that the...
  31. T

    Kelvin & Joule Link: Energy Unit Relationship?

    Is there some kind of link between the units Kelvin/second and Joule/second? I'm thinking a value in Kelvin would represent an amount of energy, just as Joule. Or?
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