Explain the following.

a. What makes tungsten the preferred material for electric lamp filaments?
 
Tungsten is commonly used as a filament in electric bulbs because of its properties. Those are
 
(i) It has .
 
(ii) It has a .
 
(iii) It is not easily .

b. What makes alloys more suitable than pure metals for use in electric heating appliances?
 
The conductors of electric heating devices are made of alloys rather than a pure metal because it has ,  and are not easily .
 
 and  is preferred as a heating element in electrical appliances such as bread-toasters and electric irons.