Question

A wire of length L and area of cross section. A was drawn into a wire of double it's length by melting it. If it's original resistivity and resistance were P and R respectively. what will be it's new resistivity and resistance?​

Answer 1

Answer:

resistivity will remain same as p.but resistance will change and become 4R

Explanation:

resistivity depends on the nature of material means which metal is it.that means copper has a certain resistivity , aluminium has certain p.etc.but resistance depends on the geometry of the substance .as in the above case the geomtry of the wire is changed so it's resistance will get changed .in the above case you might think that only length get doubled but you should observe keenly.as it is melted it's volume becomes constant.so we can write L×A1=2L×A2.SO WE GET THAT A2=A1/2.here we can write the resistance of the new wire equal to p2L/A2=4PL/A1.bt pL/A1=R.so 4PL/A1 becomes 4R.thank you.and pls follow me if you genuinely liked my explanation