CBSE - Physics - Electricity

Use the data in Table 12.2 to answer the following �
Table 12.2 Electrical resistivity of some substances at 20�C
 

	Material	Resistivity (Ω m)
Conductors	Silver	1.60 � 10−8
	Copper	1.62 � 10−8
	Aluminium	2.63 � 10−8
	Tungsten	5.20 � 10−8
	Nickel	6.84 � 10−8
	Iron	10.0 � 10−8
	Chromium	12.9 � 10−8
	Mercury	94.0 � 10−8
	Manganese	1.84 � 10−6
	Constantan (alloy of Cu and Ni)	49 � 10−6
Alloys	Manganin (alloy of Cu, Mn and Ni)	44 � 10−6
	Nichrome (alloy of Ni, Cr, Mn and Fe)	100 � 10−6
	Glass	1010 − 1014
Insulators	Hard rubber	1013 − 1016
	Ebonite	1015 − 1017
	Diamond	1012 − 1013
	Paper (dry)	1012

(a) Resistivity of iron = 10.0 x 10^-8 Ω
Resistivity of mercury = 94.0 x 10^-8 Ω
Resistivity of mercury is more than that of iron. This implies that iron is a better conductor than mercury.

(b) It can be observed from Table 12.2 that the resistivity of silver is the lowest among the listed materials. Hence, it is the best conductor.