Joules Definition and 123 Threads

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. L

    Why Is My Joules Calculation Incorrect?

    Homework Statement A steam iron draws 8.0 A when connected to a potential difference of 120 V. (a) What is the power rating of this iron? 960 W <<<<correct (b) How many joules of energy are produced in 20.0 min? 320 J <<<incorrect why? (c) How much does it cost to run the iron for...
  2. J

    2 identical capacitors, given potential in joules

    Homework Statement Capacitors A and B are identical. Capacitor A is charged so it stores 4J of energy and capacitor B is uncharged. The capacitors are then connected in parallel. The total stored energy in the capacitors is now ____.Homework Equations U = q^2/2C The Attempt at a Solution Ok...
  3. C

    How Long to Melt an Ice Cube in a Microwave with 104 Watts?

    An ice cube is placed in a microwave oven. Suppose the oven delivers 104 W of power to the ice cube and that it takes 32165 J to melt it. How long does it take for the ice cube to melt? Following my lecture notes and my textbook ... the formula should be t=(J/W), but that isn't giving me...
  4. B

    What is the electric potential energy in joules of two electrons

    Homework Statement (a) What is the electric potential energy in joules of two electrons separated by 2.43 nm? (b) What would be it be if the separation was doubled? Homework Equations i think v=kq/r The Attempt at a Solution (a) 1.185 J (b) 0.95 J i can't figure out what I...
  5. T

    Safety question: joules to pounds per square inch

    Hi there, I am the administrator for an airsoft group based out of the Chicagoland area. Many of our members currently use mesh safety goggles of the sort used in arboriculture, wood chipping, and concrete cutting. These goggles do not have a specific impact rating (though the manufacturer...
  6. D

    Calculating Joules to Compress Air: Dan's Question

    So here I am at work, and the go-to people for physics are away. Here is the problem I am trying to figure out: I'm wondering how much energy it takes to compress a certain amount of air at a certain temperature, to a certain pressure. For example, let's say I had a 4-gallon tank of STP air...
  7. S

    How to Convert Units Using OnlineConversion.com?

    how do i convert kJ to joules since that's the standard unit how do i convert mA to amperes how do i convert MV to volts
  8. B

    Izod Impact Scale Test: Determining High/Low Strength Values in Joules

    I'm supposed to determine if a bunch of materials have a high or low impact strength. I did the hard part and determined that the impact strength for each material, but I don't know a relative scale. What is a high value on the izod impact scale test(it's measured in joules). Any idea?
  9. R

    Struggling with A.P Physics Question on kWh to Joules Conversion

    This is an A.P Physics class which is algebra based and does not use calculus. This problem is really annoying because it is one of the easier questions from the homework but i can't seem to understand the procedure. One kilowatt x hour (kWh) is the amount of work or energy generated when one...
  10. A

    How many joules of electric energy are there in 1 kilowatt-hour?

    How many joules of electric energy are there in 1 kilowatt-hour?
  11. U

    Is 40,000 joules of energy enough for Nuclear fusion?

    Is 40,000 joules of energy enough for Nuclear fusion?
  12. S

    MeV to Joules Units : How? 'In Electricity'

    So Hi, how you transfer from MeV to Joules? Thx, Exam this Friday :)
  13. L

    Calculate the Joules Required to Heat 40 Kg of Water by 20°C

    Suppose you want to heat 40 KG of water by 20 degrees C How many joules of heat are required. Can someone talk me through this step by step?
  14. E

    How Long to Walk Off a Light Bulb's Energy?

    Please Help... Given: A person walks about 3.6 calories/minute. How much energy is in a 40 Watt light bulb, that is lit for 5.6 hours? Answer: I think it is 144000 J/hr. I am not sure what to do with the 5.6 hours. I think it should be used to caluculate the total J which would be...
  15. Pengwuino

    Pound of TNT to Joules Conversion: Explained and Simplified

    pound of tnt = ? Joules Does anyone know what the equivalency is? I tried to google but I get a bunch of star trek websites for some reason...
  16. J

    Calculate the energy of this photon in Joules

    I have the answer to this question but I am not exactly sure how I got it. Can you explain this to me and show me how to work it. a. When ultraviolet photons from the sun with a wavelength of 292 nm shine onto our skin they provide enough energy to break bonds in our DNA; this can result...
  17. J

    Converting kcal to joules: A simple guide

    okay I'm having a total brain freeze right now,guess it's because of all the finals I'm studying for. Anyways...I need help converting kcal to joules. Very easy I know...but I'm dumbfounded right now. I have 14.4 kcal and I need to have joules...so do I divide or multiply by 4186 J? Thanks...
  18. J

    Converting Joules to Quanta: Assistance Needed

    Hey I am in need of some assistance. In a problem I need to transfer Joules to quanta but am unsure on how to do it. A radio station is going at 200 KW with a frequency of 103.7 MhZ. So 200,000 Joules a second need to be converted to quanta. Thanks in advance!
  19. N

    How do u convert eV to joules again?

    how do u convert eV to joules again?
  20. D

    A particle with a mass of 6 MeV has energy in Joules of 6c^2?

    Just to clarify. A particle with a mass of 6 MeV has energy in Joules of 6c^2? And a particle with an energy of 3 MeV has a mass of 3/c^2 kg? And is there a way to convert this energy to a particle's charge?
  21. D

    Is it possible to have negative joules?

    Is it possible to have a negative joule?
  22. S

    Calculating Pump Motor Output: Where Did I Go Wrong?

    A pump is to lift 16.0 kg of water per minute through a height of 3.38 m. What output rating (watts) should the pump motor have? Potential Energy Initial = O Kenetic Energy Final = 0 So, KE-PE = W 1/2mv^2 - mgh = Work 1/2(16.0)(3.38)^2 - (16.0)(9.8)(3.38) = -439 W The fact that my...
  23. wasteofo2

    How to figure out the amount of heat (joules) needed to melt 1g of ice?

    So, first day of school today, and I'm in honors chemistry. I got a packet with refernce tables etc. and a homework assignment designed just to get you to use the tables and be able to connect one thing they say with another. Anyway, one question is "How much heat is required to melt 1g of ice?"...
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