Mechanical Equivalence of Heat Prelab

# Mechanical Equivalence of Heat Prelab - Matt Darling...

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Matt Darling 1/11/2014 Mechanical Equivalence of Heat Prelab The modern understanding of heat did not begin to unravel until the 1830’s in which James Joule demonstrated that heat was another form of energy instead of a fluid- like structure. Heat is traditionally measured in calories or British thermal units. This lab seeks to show that as a form of energy heat can be transferred to mechanical work. Graphing heat V. work should give a slope line that is equal to the conversion factor between joules and calories. The experiment will utilize a thermistor to measure resistance, which can be converted into temperature. Additionally, an aluminum drum will be used as a crank to slowly lift a weight connected to a string that will eventually become would around the drum as the weight is cranked up. Mechanical work is required to crank the drum and is equal to mass*g*number of turns * pi* length of lever arm. This energy is converted to heat and with the specific heat and mass of the drum one can determine heat into the system with Q = Mass*specific heat* change in
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Unformatted text preview: temperature. Ideally no energy will be lost outside the drum and the above two equations can be set equal to one another. To carry out the experiment wrap the string around the drum a couple times and begin to crank the weight up. If the weight can stay at the same level while cranking then the amount of times the string is wrapped around the drum is sufficient. Resistance is measured by a thermistor that needs to be plugged into a computer determines temperature. Determine the initial temperature before cranking, and then crank the apparatus in turns of 50 up to 400 times briefly pausing after each 50 to record time and resistance. Let the crank cool for an equal amount to time and then get another resistance reading to determine heat loss. Do work and heat calculations for each set of 50 turns. Next determine heat loss and plot mechanical work v. heat. Determine slope from this graph and check if it matches assumptions....
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