Question

The heating element of an electric heater should be made of a material having
A. High specific resistance and low melting point
B. Low specific resistance and low melting point
C. Low specific resistance and high melting point
D. High specific resistance and high melting point

Answer 1

Hint: Specific resistance basically refers to the resistance offered by a unit length and unit cross sectional area of the substance to a current when voltage is applied to it. Moreover, the melting point of a substance is the temperature at which it changes its state from solid to liquid.

Complete step by step answer:
Firstly, we will discuss specific resistance. It is defined as the resistance offered per unit length and unit-cross-sectional area when a known amount of voltage is applied. Its SI unit is ohm meter. It is basically the reciprocal of specific conductance, which is defined as a measure of a material's ability to conduct electricity. Now, let’s discuss the melting point. It is usually defined as the point at which the material changes from solid to liquid. This is the point at which both liquid and solid phases exist at equilibrium. It also varies with pressure and is specified at standard pressure.
Now, the heating element of an electric heater should be made of a material having high specific resistance and high melting point. In case of high specific resistance, a small quantity of wire is used to generate the required amount of heat or else the quantity of wire would be required higher. Moreover, a higher melting point is selected so that higher temperature is attained.

Hence, option D is correct.

Note: A compound’s melting point is determined by the force of attraction between the molecules and symmetry. Basically, the higher melting points result from stronger intermolecular interactions. Ionic compounds usually have high melting points because the ion-ion interaction of electrostatic forces is much stronger.