ThermoStat Is Real HERO

In control application for heater control temperature over current control (Overload) or day light switch, thermostat is the best to accomplish.
Thermostat is device that work for control system. It compose of two metallic strip that attracted to one sheet, so it's length is equal in normal temperature.

For use in day-light switch,we use bi-metal and heater inseries with LDR (Light dependent resistor).

The LDR has high resistance when it is in the dark (no light) , and low resistance in light (sun light). In this circuit, when day light LDR has low resistance and then current is high, so it heats the bi-metal and bend it to open circuit the lamp. When in the dark LDR has high resistance , current is low,and heater with bi-metal has low temperature,and it bend to the on state to lamp.

Another example of bi-metal, It use for heater control in electric-pot.

For this example we call it "Thermostat". It works just like in electric iron. 

Today all of electric appiance were use the temperature control with this.