Question

Electric heaters used for cooking have the filament or the heating coil on a plate made up of clay because.
(A) Clay is a bad conductor of heat
(B) Clay is bad conductor of electricity
(C ) Both A & B
(D) None of these

Answer 1

Hint: Clay is an example of a ceramic material. Hence it is a bad conductor of heat and electricity. Throughout the cross section it has good mechanical and chemical bonds that can transfer heat by the process of conduction. That is the reason why electric heaters used for cooking have the filament on a plate made up of clay.

Complete solution:
Electric heaters are based on the principle that when electric current passes through a medium heat is produced. Electrical heating is the process in which electrical energy is converted to heat energy. The principle behind Electric heating is Joule heating. The heating element is an electrical resistor, and works on the principle of joule heating. As electrical current enters a resistor electrical energy gets converted into heat energy.
The joule heating is the process by which as the electrical current enters a conductor it will release heat. And it can also be defined as ohmic heating. The heat produced is directly proportional to the square of the current multiplied by the electrical resistance of the wire.
Clay has two essential properties that are plasticity & porosity.

Hence, option (C ) is correct.

Note:
Thus an electric heater works on the principle of the heating effect of electric current. The heating element of filament blocks the electric current and does not let it pass. So the heating element gets heated and glows due to heat. It has high resistivity, so it does not melt. Thus the cord in an electric heater is a good conductor of electricity .