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Short note on: Joule experiment.

Mumbai university > MECH > SEM 3 > THERMO

Marks: 5M

Year: Dec 2013

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The main aim of Joules Experiment was to determine the relationship between the work done and the quantity of heat produced in mechanical system.

Construction and Working:

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  • The layout of Joule's experiment is as shown in the figure.

  • Paddle wheel 2 was submerged in the heat-insulated vessel 1 to the walls of which vanes 3 were fastened, the vanes interfering with the motion of water due to rotation of the paddle.

  • Rotation was imparted to the paddle (stirrer) by the falling load 4 of weight G, connected to the paddle by means of a rope and pulley 5.

  • As the weight falls through a distance Δh, the work done by it (and, consequently, by the stirrer) is equal to the decrease in the potential energy of the weight GΔh.

  • The heat liberated in the water-filled vessel is calculated from the rise in water temperature, measured with a thermometer.

Importance of Joule’s Experiments:

  • Joule’s experiments conclusively established that heat is a form of energy.

  • Always the same amount of heat was produced by spending a given amount of mechanical work. It is immaterial what type of arrangement is used for doing mechanical work.

  • It defines the relationship between Joule and Calories.

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