Mumbai university > MECH > SEM 3 > THERMO

Marks: 5M

Year: Dec 2013

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:

• 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.