How does an Electric Iron works and what’s inside it? (with live preview)

If you have ever wondered why an Electric iron turns on and off all by itself, then you are at the right place. Because in this post, you will see a teardown of an Electric iron, what’s inside it, and learn how does an Electric iron works. 

I had this old – very old electric iron for a long time now. So for science, I am going to open it and show you how does an Electric iron works.

You can watch the video given below or continue reading the article.

Parts inside the Electric Iron:

 

 

Thermostat inside the Electric Iron:

 

 

• A thermostat is a device that changes its orientation with the increase in temperature.
• This thermostat consists of a Bi-metallic strip. And as the name itself suggest, Bi-metallic means two metal strips.
• Each of the two strips has a different coefficient of thermal expansion. One has a higher whereas the other has a lower coefficient of thermal expansion. So that one bends more than the other metallic strip at any particular temperature.

• In the image given above: at a higher temperature, Metallic strip 2 bents and pushes the Metallic strip 1 upward to a position where the electric connection between strip 1 and live wire breaks. And Electric iron gets turned off.

 

Heating element inside the iron:

• A heating element is the heart of any electric iron. It consists of a nichrome wire placed inside the mica sheet.

 

• This nichrome wire heats up as current passes through it due to I²R loss. So longer the time of flow of current through it, the more is the heating of the Heating element.
• Mica is chosen as a cover in a heating element because: 
• (a) It is a very good insulator and (b) It can withstand a very high temperature.

 

Turning knob or tightening screw:

 

 

• Using this knob, we can adjust the temperature of the electric iron according to our needs.
• This knob is connected to a screw that controls how hard the contact or upper metallic strip must bend to separate and break the electric connection so that the Electric iron gets turned off.
• This means if I keep turning the screw, then the temperature required to bend this upper metallic strip also increases or you can say the temperature required to break the electric connection increases.

 

Neon bulb:

• This bulb is used as an indicator for Electric iron.
• It is connected in parallel to the heating element.

 

Working of an Electric Iron:

**Watch the video given above to see the Electric iron in action

• An electric iron is first connected to the power supply.
• The neon bulb lights up indicating the start of heating process in the heating element.
• Let’s say the knob is at its lowest position right now. In this case, as soon as the temperature of strip 2 rises to 100 degrees(let’s say); it bends enough to break the electric connection between strip1 and the live wire.
• Now the electric iron is off.
• After some time, strip 2 contracts to its original position, and thus the electric connection is made again causing the Electric iron to turn on.
• Now let’s say the knob is at its uppermost position. In this case, as soon as the temperature of strip 2 rises to 200 degrees(let’s say); it bends enough to break the electric connection between strip1 and the live wire.
• Now the electric iron is off.
• After some time, strip 2 contracts to its original position, and thus the electric connection is made again causing the Electric iron to turn on.

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