Experiment:Determination of the value of the mechanical equivalent of heat (J) by electrical method.

Experiment No : 03
Name of the Experiment:
Determination of the value of the mechanical equivalent of heat (J) by electrical method.
Theory:
The mechanical equivalent of heat J is the amount of electrical energy required to generate one calorie of heat. If E volt be the potential difference across a conducting coil (Fig. 3.1) and i ampere be the current flowing through the coil for t seconds, then the electrical energy in the coil is Eit. If this energy is converted into heat H(calories) then the mechanical equivalent of heat Jis
J= Joules/Calorie H
(1)
If His measured by means of a calorimeter with its contents where the temperature raises from C to 2°C then
H = (Ms+W) (02-01).
where M is the mass of the water in the calorimeter, s is the specific heat of water and W is the water equivalent of the calorimeter and stirrer. W can be calculated from the mass and specific heat of the calorimeter and stirrer.
From equations (1) and (2), we get
J = Eit/{(Ms+W)(02-01)}
Joules/Calories