a. Table gives the resistivity of three materials in (in Ω m) A, B, C.

Which one of them is the best conductor? And which is an insulator and why?

b. A wire of resistivity P is stretched to twice its length. What will be its new resistivity?

( CBSE 2012, 2011)

a. Conductor has very low resistance in order to allow the free flow of electrons through them. Therefore Material A is the best conductor because it has the low resistivity which implies low resistance.

Insulators are the materials having high resistance. Therefore Material B is the insulator because it has the highest resistivity which implies high resistance.

b. The Resistivity of the wire will not change with the change in length. Resistivity is a property of the wire, it doesn't depend upon it’s length or cross-sectional area.