# Thermal Fan

 Physics, Engineering: Properties of Metals, Seebeck Effect Grade Range: Middle School, High School Format: Hands-on

This is a quirky little demo that students may have trouble understanding. Bring plenty of extra ice to keep the cold beaker cold, otherwise this demonstration may end early!

## Materials

• Thermal Fan & Box
• Hot Plate
• Water
• Ice
• Two 250mL Beakers

## Safety Precautions

Please read the General Safety Precautions section of the Demonstration Safety page before performing this demonstration.

## Demonstration

1. Fill a beaker with water and set it on the hot plate, then set the hot plate to the highest temperature setting. Fill the second beaker with ice and water, and set it on top of the Thermal Fan Box next to the hot plate.
2. Once the water on the hot plate is near boiling, slide the beaker on the hot plate closer to the one on the box. Put a leg of the Thermal Fan in each beaker, and set it in gently. After 20-30 seconds, start nudging the fan blade to help it start to spin. It will start spinning on its own!
3. Answer questions for students and provide a brief explanation for the demo to them. Keep adding ice to the ice water and water to the hot water so the fan can keep running.

## Why This Works

The Thermal Fan is a classic demonstration that shows an energy transfer. The Seebeck Effect is when an electric potential is produced across a metal surface due to a difference in temperature. As heat energy is transferred through the metal, the heat energy has a corresponding electric current. This effect is seen with the Thermal Fan as it starts to spin. The fan has a leg in boiling water and a leg in ice water. As the heat travels from the boiling water to the ice water, it passes through a circuit in the center, which is connected to the fan motor. This circuit can detect the electric current produced by the temperature difference, and since one leg has a low electric potential and the other has a high electric potential, the circuit will collect and use the electric current to power the fan, making it spin!