Stored Energy Home Experiment

This is a simple experiment that illustrates power converting to heat energy and thermal energy loss. The loss of energy measured in this experiment can be related to energy loss in a plasma experiment.


  1. A microwave oven (a bunson burner and beaker may work)
  2. Two identical microwave-safe mugs
  3. A cooking pan, say 9"x9", or a cooking skillet
  4. Water at or near room temperature
  5. A thermometer accurate to within 1 or 2 degrees to measure the water temperature
  6. OPTIONAL: Graph paper or a graphing computer program (EXCEL works well).

Hypothesize First

  1. Guess how hot 2 cups of water will get from 2 minutes in a microwave.
  2. (for extra credit) Calculate how hot 2 cups of water will get from 2 minutes in a microwave.
  3. Guess how the hot water in a cup and in a pan will cool in 10, 20 and 30 minutes. (Will the plot of temperature decrease be a straight line?)
  4. What could invalidate the calculations for this experiment?

Make sure you know how to operate a microwave oven SAFELY!


  1. Put 8 ounces of cold tap water in each of two identical mugs.
  2. Measure the temperature and record it.
  3. Place each cup side by side in a microwave (place each cup the same distance from the center of the microwave for equal heating).
  4. Heat for 2 minutes.
  5. Measure the temperature and record it.
  6. Pour the water from one cup into a cooking pan or skillet.
  7. Every 5 or 10 minutes, measure and record the time and temperature (you may have to pour the water from the pan back into the cup for measuring).
  8. Continue measuring for 30 to 60 minutes.
  9. Plot the results on a graph with seconds along the horizontal axis and temperature along the vertical axis.


  1. If you moved water from the pan to a cup for measuring the temperature, repeat the experiment but leave the water in the pan for a full 30 minutes (i.e., don't it pour back and forth) and see if the results change.
  2. Perform the experiment with a different type of thermometer.


  1. How do the results differ from what you expected?
  2. How much energy was injected into the water by the microwave?
  3. What is the power of the energy loss from the water during the first few minutes of cooling?
  4. What are the "forms of energy" flow in this experiment?

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