Mechanical. Equivalent of Heat Tube

Transcription

1 Mechanical Instruction Manual Manual No A Equivalent of Heat Tube Model No. ET-8781

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3 Equivalent of Heat Tube Model No. ET-8781 Table of Contents Equipment List... 3 Introduction... 4 Theory... 4 Equipment Setup... 5 Suggested Experiment... 6 Sample Data/Results... 7 Appendix A: Technical Support... 8 Appendix B: Copyright and Warranty Information

4 Model No. ET-8781 Mechanical Equivalent of Heat Tube Equipment List Mechanical Equivalent of Heat Tube Model No. ET Included Equipment *Use Replacement Model Numbers to expedite replacement orders. Replacement Model Number* 1. Mechanical Equivalent of Heat Tube(1) ET Fast Response Thermistor Probe (1 built-in probe) PS Metal Balls (120 balls) Velcro Strip Additional Equipment Required PASCO computer interface (PASPORT or ScienceWorkshop ) DataStudio software (version or later) Temperature Sensor A computer Replacement Model Number Various (See PASCO catalog.) Various (See PASCO catalog.) PS-2125* or PS-2143* or PS-2146* or CI-6527A** NA * PASPORT sensors requires a PASPORT interface. ** ScienceWorkshop sensors require a ScienceWorkshop interface. 3

5 Mechanical Equivalent of Heat Tube Model No. ET-8781 Introduction PASCO s Mechanical Equivalent of Heat Tube (ET-8781) is used for demonstrating changes in gravitational energy to thermal energy. While the energy conversion is occurring, students can measure and observe the temperature change in real-time in a DataStudio display. As the tube is turned over, the steel balls fall the length of the tube and strike the thin, metal plate at one end. Fastened to the bottom of the metal plate is a fast-response thermistor for continuously measuring the temperature of the plate. The thermistor can be directly plugged into either a PASPORT Temperature Sensor or a ScienceWorkshop Thermistor Sensor. Students can then use DataStudio to measure the temperature increase caused by the impact. In addition, students can measure the mass of the falling balls and the distance over which they fall to calculate the change in gravitational energy. The Mechanical Equivalent of Heat Tube is typically used in conservation of energy studies. The tube can also be used as an analogy for the disappearance of kinetic energy during a collision. Theory m b = mass of the steel balls m p = mass of the aluminum plate c b =specific heat of the steel balls c p =specific heat of the aluminum plate T=change in the temperature L=length of the tube Q=thermal energy (heat) PE= gravitational potential energy Potential Energy The change in gravitational potential energy of the balls as they fall a distance h is given by PE=mgh. If the tube is held vertically at its center and rotated 180 degrees, the balls fall a distance of L, the length of the tube. If the tube is then rotated back to the initial position, the balls again fall a distance of L. Note that it is important that your hand stay at a constant height during rotation. Thus, the balls fall a total distance of h=2l for each back and forth rotation, and the total change in gravitational potential energy of the balls is PE=m b g(2l) (1). 4

6 Model No. ET-8781 Mechanical Equivalent of Heat Tube Thermal Energy When the balls strike the aluminum plate, their kinetic energy is converted into thermal energy, increasing the temperature of the plate and the balls. For a single object, Q=mc T, but since the balls and the plate have different specific heats, we need to account for each. Also, there are two identical plates. You cannot remove the bottom plate. It is assumed that T is the same for all of the objects. Q=[m b c b + m p c p ] T (2) Equipment Setup 1. Plug the stereo plug of the Mechanical Equivalent of Heat Tube into a PASPORT Temperature Sensor or ScienceWorkshop Thermistor Sensor. 2. Plug the Temperature Sensor into a PASPORT computer interface. (Note: If you are using a ScienceWorkshop interface, plug the Thermistor Sensor into an analog channel of a ScienceWorkshop computer interface. From the Sensors list, drag the Thermistor icon to the same channel in the Setup window. 3. Use the Velcro strap to hold the cord against the tube. 4. Click the Start button. Turn the tube upside down and back up again. Repeat several times. Watch the temperature change in DataStudio. To stop data collection, click the Stop button. Note: Do not use the Mechanical Equivalent of Heat Tube in direct sunlight. Using the tube in direct sunlight will skew your results. Figure 1: Heat Tube connected to a Temperature Sensor and a PASPORT interface 5

7 Mechanical Equivalent of Heat Tube Model No. ET-8781 Suggested Experiment Exploring Energy Changes During the Rotation of a Heating Tube Equipment required: Mechanical Equivalent of Heat Tube (ET-8781), DataStudio software, computer interface (PASPORT or ScienceWorkshop), Temperature Sensor Note: The Heat Tube must be used with a Temperature Sensor that accepts a stereo plug input (i.e. PS-2125 Temperature Sensor, PS-2143 Quad Temp. Sensor, PS-2146 Absolute Pressure/ Temp. Sensor, or CI-6527A Thermistor Sensor) 1. Connect the Heat Tube to a Temperature Sensor and computer interface (For instructions, see steps 1 and 2 under Equipment Setup. ) 2. Launch DataStudio. In DataStudio s Experiment Setup window, set the sample rate to as fast as possible. In the Data list, double click on the Temperature icon to open the Data Properties dialog. In the Data Properties dialog, set the accuracy to 0.01 and the precision to 2. Click the OK button. 3. Pull off the cap on the heating tube. Weigh the mass of enough steel balls to cover one layer on the surface of the aluminum plate on the inside of the tube. 4. Remove the aluminum plate from the plastic cap. Weigh the plate. 5. Put the balls in the tube. Reinsert the aluminum plate and push the cap back tight on the tube. 6. Measure and record the length of the tube. 7. In DataStudio, open a Graph display and click the Start button. Hold the Heat Tube upright in a vertical position with the cord end at the bottom. Hold the tube in the center with your hands over the Velcro strap. Keep your hand at the level on the tube. Turn the tube upside down and back up. Watch the temperature change in DataStudio. 8. Rotate the tube back and forth three times. Record the biggest change in the temperature. (Note: To record the change, use the Smart Tool. In the Graph display, click on the Smart Tool button. Hover the pointer over the box until the pointer becomes two double-headed arrows. Drag the arrows to the desired location. The x and y coordinates appear to the right of the arrows. 9. Calculate the loss in gravitational potential energy for one back and forth motion. Use equation 1 for the calculation. 10. Calculate the increase in thermal energy of the balls and plates for the largest temperature change, T, using equation 2. 6

8 Model No. ET-8781 Mechanical Equivalent of Heat Tube 11. Calculate the percentage of energy turned into heat using %=Q/PE x 100(%). 12. Where did most of the energy go? 13. Repeat steps 3-12 with twice the number of balls and one-half the number of balls. 14. How does the temperature and potential energy (PE=mgh) change when you change the number of balls? Why? Explain your results. Sample Data/Results 7

9 Mechanical Equivalent of Heat Tube Model No. ET-8781 Appendix A: Technical Support For assistance with the ET-8781 Mechanical Equivalent of Heat Tube or any other PASCO products, contact PASCO as follows: Address: PASCO scientific Foothills Blvd. Roseville, CA Phone: (916) FAX: (916) Web: Appendix B: Copyright and Warranty Information Copyright Notice The PASCO scientific A Mechanical Equivalent of Heat Tube Manual is copyrighted and all rights reserved. However, permission is granted to non-profit educational institutions for reproduction of any part of the A Mechanical Equivalent of Heat Tube Manual, providing the reproductions are used only for their laboratories and are not sold for profit. Reproduction under any other circumstances, without the written consent of PASCO scientific, is prohibited. 8

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