Question

6. (a) Name a conductor, an insulator, a semiconductor, a ductile material and a brittle material. (b) What are the units of electrical conductivity and ductility? (c) What is the difference between 24 carat gold and 18 carat gold in gold purity? (d) What is the benefit of alloying gold with copper in gold rings? I

Answer 1

6.(a) Conductors are the substance that transmits heat or electricity through them. The substance or materials that may act as a conductor, as well as insulators under different conditions are known as semiconductors. Insulators are the substance that does not allow heat or electricity to pass through them.

SO the common examples of conductore are Copper,silver ,gold,aluminium,etc.

Insulators: Glass,wood ,rubber,air,etc

Semiconductors: Antimony,arsenic,germanium,boron,etc

Ductility: Ductility is the ability of a solid material to deform under tensile stress. Practically, a ductile material is a material that can easily be stretched into a wire when pulled .For example, copper,aluminium,steel

Brittleness: This is basically the opposite of ductility where a material breaks when tensile stress is applied to lengthen it.For example, cast iron,concrete,glass products,etc.

(b) SI unit of electrical conductivity is siemens per meter (S/m) or mho which is determined by unit of inverse of resistivity.

Ductility can be expressed as strain, reduction in area, or toughness. Strain, or change in length per unit length, Change in area per unit area.Thus it is a dimensionless quantity

(c) 24 karat gold contains 24 parts pure gold.18 karat gold contains 18 parts pure gold with 6 parts of other metals added as an alloy.So in terms of purity,24 carat gold is pure form of gold while other carat can be considered as mixture.In other words,if you consider gold as 100 part then for 24 carat gold it occupies all 100 part.While for 18 carat gold,out of 100, 18/24 part of 100 is only gold.

(d) When pure gold is used,it is simply a metal.But when it is mixed with other metals like alloy,the properties of gold are enhanced because of alloy as it provides greater strength and hardness to the mixture.Apart from this copper shows resistant to the corrosion and thus make the durability of gold.Hence,copper is mixed with gold for forming weeding rings.