Purpose:Demonstrate adiabatic expansion of air by plotting the temperature.
Description:A tightly corked bottle containing air with a small amount of water is pressurized using a bicycle tire pump. When the cork pops the air expands adiabatically, cooling sufficiently to form fog in the bottle. The computer plots a graph of the air temperature in the jar using a thermistor probe, as seen in detail below. As air is pumped into the jar the temperature slowly rises; when the cork blows the temperature suddenly falls to below its initial level. The graph can be displayed on video projectors in the lecture hall.