05.06.2016
Written By: Harishankar Natesan
Today, we talked about how heat travels both in the presence of media such as solids (conduction) and fluids (convection) as well as the absence of media (radiation). First, we demonstrated the heat transport using balls. Volunteers were asked to stand in three different configurations representing solid, fluid and vacuum. Balls were passed in each configuration mimicking heat. For heat transport in solids (conduction), the volunteers were standing together and passed the balls without moving. For heat transport in fluids (convection), the volunteers were standing further apart and the person with the ball moved and passed the ball. For heat transport in the absence of media (radiation), volunteers threw the ball.
Next, we divided the students into 5 groups doing three experiments each in conduction, convection and radiation. For conduction, the students were asked to fill a balloon with different materials like air, water, corn syrup and sand and were asked to pop the balloon with the help of a candle. Initially, they had difficulty in popping the balloon as the candle flame was not powerful. Soon, some groups started using multiple candles. For convection, the students were looking at mixing of hot and cold water visualized with the help of food coloring agents. They filled a 100 mL conical flask with hot water and immersed inside 900 mL beaker filled with water at room temperature. The students observed hot water rising up and mixing with water in the beaker. Then the students repeated the experiment with the conical flask filled with cold water (adding ice). After immersing in beaker, the cold water did not rise up and mix with water in the beaker. Finally, the students worked on radiation, where they had an opportunity to use infrared cameras. Using IR cameras, they looked at different objects like candles, metals, plastics etc. and also took pictures of themselves. Finally, the entire group took a group picture using IR camera and was projected in the classroom.