# Demo Content

Thermoelectric Converter

Purpose:
To demonstrate the relationship between the first and second laws of thermodynamics.

Equipment:
Two thermoelectric converters, one with electrical plugs Hot and cold water source (the water cooler in the physics office should be sufficent) Two cups Power supply (around 5 or 6 volts is perfect, you should be able to find one that will work in one of the Mara closets)

Equipment Location:
Mara_Left

Procedure:
First get two cups of water. One hot and one cold. Take the fan and place one leg of the fan in each of the cups. After a short period of time the fan should start to turn and continue to turn for a period of time. Then take the fan out of the two cups and combine the water so that you have two cups of water with equal temperatures. If you place the non moving fan into these two cups the fan will not move. For the last part place the fan with the electrical plugs into the two cups of equal temperature waters. When the fan is plugged in and the switch says E to delta T one of the legs of the fan will become cold while the other becomes hotter at the same time. Since you are not supposed to leave the fan plugged into the power source for more then 2 minutes it will not be enough time to change the temperature much but the temperature difference should be very evident to the touch.

Hints:
It does take some time for the fan to start turning so some patience is needed. You may want to place the fan in the water while you are still lecturing and refer back to it when it starts to work. You may also need to start the fan moving if it can not overcome the static friction after a minute or two. Also you should not leave the fan with the electrical plugs dependent on the electricity for more then 2 minutes.

Relevant derivations/explanations:
This experiment shows the relationship between the first and second laws of thermodynamics. The first law states that energy can not be created or destroyed but it can be converted from one form to another. The second law clarifies that in some ways by stating that the direction of heat flow is in a specific direction. The heat flows from the areas of more internal energy to the areas with lower internal energy, or from hot to cold.