Question

(i) All metals are electrical conductors. True / False (ii) All ceramics are electrical insulators. True / False (iii) All polymers are electrical insulators. True / False (iv) For regular ceramic materials, yield strength and ultimate tensile strength are the same. True / False (v) Crystal systems are defined by the shape of the lattice and the atom positions. True / False

Answer 1

(i) All metals are electrical conductors. True  

(ii) All ceramics are electrical insulators. True  

(iii) All polymers are electrical insulators. False  

(iv) For regular ceramic materials, yield strength and ultimate tensile strength are the same. False

(v) Crystal systems are defined by the shape of the lattice and the atom positions. True  

Explanation:

(1) Generally, all metals exhibits good conductance of heat as well as electricity. They exhibit this property due to the valence mobile electrons in their outermost shell. Due to their mobile nature, they conduct heat as well as electricity.

(ii) In general, ceramics is a good insulator. Most of the ceramic material resists the flow of heat or electricity and thus finds extensive application in high voltage equipment.  

(iii) Polymers exhibit hybrid property. By hybrid, I mean to say they display the property of insulator, semiconductors as well as conductors in some cases. Since the composition of polymers depend on the constituting ingredients hence if the parent material is good conductors, polymers can act as conductors.  

(iv) Yield strength can be referred to as the critical strength from where the body exhibits a plastic state of deformation. Yield strength is thus the ultimate strength beyond which any element breaks. Hence for ceramics yield strength is always more than the tensile strength  

(v) Crystal system refers to a description of the arrangement of ion, an atom in a structural lattice. The atom's placement in a crystal and the shape of lattice influence the crystal system.