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Joule’s Experiment

General Aim of Joule’s Experiment

1- Determine the value of the mechanical equivalent of heat coefficient through Joule's experiment.

2- Determine the value of coil resistance in the calorimeter virtual lab.

 

Method of Joule Experiment

Conversion of electrical energy into heat energy in Joule heating simulation.

Theoretical Background/Context

• When an electrical current passes through a resistive element (coil), which is completely immersed in water, we can state Joule’s law of heating to explain the energy transformation.
• Electrical energy is dissipated within the element that is transformed into heat energy. 
• This causes the temperature of the element to rise by an amount that is proportional to the time interval, voltage and the current passed through the element. 
• Applying the principle of conservation of energy, we can determine the mechanical equivalent of the heat coefficient and the resistance of the resistive element.

Principle of Work

In Joule's experiment, the following steps is implemented:

• A certain amount of water is added to a calorimeter of known material and mass, as performed in the Joules calorimeter experiment.
• A heater coil is inserted into water that is connected to a power supply, an ammeter, and a voltmeter. Measuring the initial temperature for water. 
• After switching on the power supply electrical energy introduced by the power supply is converted into heat energy that causes the rise in the temperature of water.
• Waiting 15 minutes and switching off the power supply then watching the thermometer until it reaches the maximum value (final temperature). 
• By some calculations, we get the mechanical equivalent of heat and the coil resistance.