Question

An aluminum wire of 1 mm diameter is surrounded by a copper sheath of 1 mm thickness. What is the resistance of 10 m of this wire?

A. 0.78

B. 0.39

C. 0.025

D. 0.061

Answer 1

So resisitance of aluminium wire first we evaluate

Now as l =10m

A is cross section area of wire

and resistivity of aluminimum

so plug in all values in formula we get

and For cooper

cross section is

and resistivity of copper

So resistance we determine from formula

and they are connected in parrallel so net resistance is

So,

Option c)