Question

Why is the heating element wound on a mica sheet and kept in between two mica sheets in an electric iron box?

Answer 1

Hint:Electric iron box is the conventional iron that is used for ironing.It says that when an electric current is passed through a piece of wire, the wire gets heated up.

Step-by-Step Explanation:
Step I:
Mica is a good conductor of heat. It protects the filament from the outer body of electric iron. Mica protects the filament because if in case the electric current passes through electric iron and it becomes accidentally live, then it breaks the insulation and protects the filament from burning out.
Step II:
Also mica is a bad conductor of electricity. Due to this reason it can tolerate high temperature. Mica provides high thermal resistance as it is a good insulator. Therefore, these properties of mica are suitable to use in an electric iron.
Step III:
When an electric iron is switched on and the current is made to pass through it, then while working, then it transfers the heat from the filament to the plate of the iron. Mica transfers the heat by the process of radiation. Radiation follows the law of optics. So electromagnetic waves can reflect and refract if they come in contact with a medium. Since mica is transparent, therefore it allows transfer of heat through radiation.

Note:Infrared radiation of light is used in electric iron and other heating elements. It is to be noted that mica is not used in the electric iron these days. Nowadays nichrome wire that is enclosed in a stainless steel tube is used. The insulator used is magnesium oxide between them.