HOW DOES THE EXPANSION OF SOLIDS HELP TO OUTO OFF IN IRON BOX???
The bimetallic strip used in the iron boxes is responsible for the auto-off. This technology uses two thin strips of different metals - such as copper and iron, copper and steel and brass and steel - bonded together and rolled into a coil. As the temperature rises, the different metals expand at different rates, causing the strip to bend. When the strip bends enough to touch an electrical contact and complete an electrical circuit, it turns on the heating system. If the temperature changes enough to unbend the strip, contact is lost, this interrupts the circuit and the system is turned off and can be reset when the bimetal strip has cooled down.