Workout: Heat transfer

Read

Read the web page Heat transfer.

Launch

To give you some sense for how this works, go to the PhET simulation, "Energy Forms and Changes".

Set up

Make sure you're on the Energy Systems tab. Turn on the "Energy Symbols" box at the upper right. For the sources of energy inputs to the system, choose the heated teakettle from the options bar on the bottom. For the energy transformer, choose the electric generator (wheel). For the application, choose the light bulb. Your screen should look like shown at the right.

Answer these questions

1. Now turn the heat up to maximum and watch what happens. Is the total number of energy units conserved or not? Energy enters the system as thermal energy from the heater. Describe the transformations in the energy that occurs
2. Watch the energy units flowing out of the teakettle through the steam. Why is it both mechanical and thermal? What happens as time goes on?
3. Now switch the source to the bicycle and describe the energy flow. Let it run long enough to see the "Feed me" button appear. What's that all about? 
4. Estimate the efficiency of the incandescent bulb shown by counting the number of light energy packets emitted compared to the number of thermal energy packets emitted. Replace the incandescent bulb by the fluorescent bulb. Did the programmers program this bulb to be more efficient than the incandescent bulb or less? By how much? 

Joe Redish, Fall 2016.