Porcelain

Ceramic

Ebonite

Bakelite

Near the outer seating

Inside a hollow tube

Out side the body

Below the body

For the uniform distribution of heat

To prevent the heating element from coming out of grooves

To reduce the space for coiled heating element

To increase the resistance of the heating element

Copper

Silver

Aluminium

Brass

Low co efficient of expansion

Low specific resistance

Low mechanical strength

Low voltage withstanding