Thermostat
Safety Warnings
Warning: Open Flame and Hot Surfaces
Warning: Electrical Safety
Purpose
Demonstrates how differential thermal expansion of a bimetallic strip creates mechanical switching in a thermostat circuit. Heating the strip causes it to bend, switching which of two indicator bulbs is lit -- illustrating the operating principle of mechanical HVAC thermostats.
Figure 1:
Thermostat demonstration at room temperature with both bulbs off. The bimetallic strip at top controls which bulb receives power.
Figure 2:
After heating: the bimetallic strip bends and switches the circuit, lighting the right bulb.
Figure 3:
After cooling: the strip returns to its original position, switching back to the left bulb.