TOPIC:

ID Code: I2-45
Purpose: Brainteaser regarding convection.
Description: Two candles, one on the desk and one raised about 30 cm, are lit and then covered by a tube about 50 cm high and 10 cm in diameter. The tube is sealed at the top by a dark plastic cover so that no air may flow into the tube as the experiment progresses. Which candle will go out first, or will they go out simultaneously?

The answer can be seen in the sequence of photographs above. The photograph at the left was taken after the candles were lit but before the tube had been put in place over the candles. The left center picture was taken immediately after the tube was placed over the candles. The center photograph was taken after about one minute. The right center photograph was taken after about 1.5 minutes, and the photograph at the right was taken after about 2.5 minutes, showing the order in which the candles became extinguished.

Availability: Available

See the Physics Question of the Week for 4 May 2015 for an example of how this demonstration can be used in class interaction and discussion: lecdem.physics.umd.edu/question-of-the-week-archive.html