1. HEAT AND JOULE’S EXPERIMENT
GROUP HENRY:
Jelita Bungin
Siti Noor Yusof
Soh Wei Ing
Mohd Farhan Abdul Razak

2. HEAT
A form of energy that is transferred from one body (system) to another body (system or surroundings).
It exists only as energy in transit between a system and its surroundings.
Heat transfer can occur when there is a temperature difference.
The heat transfers from the hotter body to the colder one. This will continue until the temperature of the bodies are the same (thermal equilibrium).
The SI unit of heat is joule (J).

3. Other units are:
1 cal (calorie) = J
1 Btu (British thermal unit) = J
Thermie = 4.184E6 J
ft.lbf = J
kJ = 1000 J
MJ = 1E6 J
hp.h (horsepower.hour) = E6 J
kWh = 3.6E6 J
MWh = 3.6E9

4. Joule’s Experiment

7. The modern concept of heat developed following crucial experiments carried out by James P. Joule ( ), in the cellar of his home near Manchester, England, during the decade following 1840.
In Joule's Experiment, he created a contraption whereby he could measure mechanical energy and at the same time thermal energy (temperature).

8. It was well known that heat and work both change the energy of a system.
Joule conducted a series of experiments which showed the relationship between heat and work in a thermodynamic cycle for a system.

9. Procedure:
1. He used a paddle to stir an insulated vessel filled with fluid. The fluid is made up by known amount of water, oil, and, mercury.
2. The amount of work done on the paddle was noted (the work was done by lowering a weight, so that work done = mgz).
3. This vessel was placed in a bath and cooled. The energy involved in increasing the temperature of the bath was shown to be equal to that supplied by the lowered weight.

10. He found for each fluid that a fixed amount of work was required per unit mass for every degree of temperature rise caused by the stirring, and the original temperature of the fluid could be restored by the transfer of heat through simple contact with cooler object.
Hence, we can conclude that heat is a form of energy.
Joule also performed experiments where electrical work was converted to heat using a coil and obtained the same result.

11. The mechanical energy is the potential energy of the masses
The mechanical energy is the potential energy of the masses. This is what heats the water. Joule discovered that:
the loss in  mechanical energy is proportional to an increase in temperature of the water and the amount of water used
the constant or proportionality (that makes the loss in mechanical energy equal to the increase in temperature of the water) was found to be J/(g·ºC)