Joule Heat Laboratory Report

Topics: Heat, Thermodynamics, Energy Pages: 6 (692 words) Published: May 7, 2014
PHYS 124 – 3:30 Th
Lab 5: Joule Heat
John Doe

4/3/2014

Introduction
The objective of this lab is to learn that whenever there is an electrical current in a conductor, there is some electrical energy that is converted into heat energy. The heat generated in an electrical circuit is commonly referred to as joule heat. Sir James Joule studies of these separate phenomena lead him to the discovery of the proportionality constant known as the Joule equivalent of heat, denoted by J. The Joule equivalent of heat is the amount of mechanical or electrical energy within a unit of heat energy. In many electrical applications joule heat is an undesirable loss of energy. However toasters and electrical heaters are purposefully converted into heat energy. In this experiment, the heating effect of electrical current and the electrical equivalent of heat will be investigated. The primary goal of this experiment is to show how the concept of heat energy relates to electrical energy

Materials and Method
In order to complete this experiment we used a combination of electrocalorimeter (immersion heater and calorimeter), power supply, ammeter (0 to 3 A), voltmeter (30 V), rheostat, connecting wires, thermometer, stopwatch, laboratory balance, and ice. In order to obtain the data, the DataStudio™ software is set up on the computer to use the temperature sensor on the apparatus to collect steadily the temperatures at specified time interval of 5-seconds. After the computer is completely set-up, the rest of the apparatus is collected. Water is added to the calorimeter until it is about 2-inches away from being completely full. In order to lower the temperature of the water, a few ice cubes are added. Once the ice is completely melted, the calorimeter is cautiously placed into the apparatus to ensure that they heating-coil and temperature probe do not touch. The voltage is set to a constant amount of approximately 6-volts. The voltmeter is wired directly to the heating coil assembly and is used to gain an accurate measurement of voltage between the two ends of the heating-coil. The computer is now ready to collect the data. While the data is recorded into the computer directly from the temperature probe, the stirrer rod is constantly moved up and down to stir the water as it is heated. This ensures that all the water and its container will come into thermal equilibrium with each other. The data acquisition stops automatically after ten-minutes. The results are graphed in the plot, temperature vs time. Results

Mass of container and water
mcw = 278.0 grams
Mass of container
Mc =42 grams
Specific Heat of Water
Cw= 1 kcal
Specific heat of aluminum
Cc= 0.21 kcal
Voltage drop across heater coil
V = 6.1 V
Current flowing in heater coil
I= 4.82 C
Slope of temperature vs. time
m= ∆T/∆t = 0.025 = 6.5 E-5
Joule Equivalent of Heat
J = 4792.37 J/kcal
J= 4817.36 J/kcal

% Error
%Error = 14.5%
%Error = 15%
Calculations:

J= 4817.36 J/kcal

% Error = * 100

% Error = * 100
% Error = 14.5%

Discussion
Looking back to the hypothesis we were able to show how the concept of heat energy relates to electrical energy. While doing this experiment we came across some errors that could stem from multiple sources. For example, the minute presence of ice not totally melted might have been existent when the experiment begins. This would cause a much cooler temperature than expected at the indicated voltages and current readings. Additionally, the mass of the water and container might be skewed due to the presence of ice. Ice is less dense than liquid water and this would cause inequality in the data used to calculate the joule equivalent of electrical energy  Conclusion

This experiment demonstrated the relationship between the equivalence of electrical energy and heat...
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