Mechanical Work of Heat
Physics 2426
Date 9/19/2011
mechanical heat lab
Objectives
The objective of this experiment is to determine experimentally where the heat comes from and how is it created; also to understand what the relationship between mechanical energy, electrical power and joule heating coming from a resistor submerged in water. Furthermore comprehend how to use an electric circuit depending on the use of an ammeter or a voltmeter using a parallel and a series circuit respectively. By the termination of this experiment we will be comfortable working with basic circuits.
Concepts
Historically the mechanical conversion of heat has been a concept with a great importance in the development of the conservation of energy and thermodynamics in science. The mechanical conversion of heat states that heat and motion are equally exchangeable and that always, an amount of work would generate the same amount of heat; the total work is then converted to heat energy. This is statement is the outcome of the first Law of Thermodynamics, which states that W ∝ H or W = J H The conversion factor between electric energy measured in joules and heat energy in calories is called the electrical equivalent of heat
1 cal(calorie) = 4.186J (joules) or Kj =4.186J/cal
In this particular experiment we will reexamine the value of Kj. Other basic SI units involved in this experiment are:
Coulomb ( c) : unit for electric charge
Ampere(A) unit for electric current, flow rate of charge, A=C/s
Volt(V) unit for electric potential, energy/coulomb, V=J/C
Watt(W) unit for power, energy/ time, W=J/s
The increase of the temperature of the wire is the result of the electrical energy transferred to thermal energy. When a charge is being pushed by a potential difference throughout a circuit, it build up an energy known as Qv. Then the work produced by voltage source is W = qV and the power degenerate in the wire is then P = W/t. Knowing that the current is the charges rate throughout the conductor the power generated can be also written as P = IV
We started by assembling the electrical circuit diagram, positioning the DC power supply underneath the voltmeter and ammeter, we plugged the cables to make the voltmeter circuit in series and the ammeter in parallel, then we proceed to change the voltmeters scale to 25Vand the ammeter to the 10A scale.
We took