Question

Two conductors are made of the same material and have the same length. Conductor A is a solid wire of diameter 1mm. Conductor B is a hollow tube of outer diameter 2mm and inner diameter 1mm. Find the ratio of resistance RA to RB. NCERT Class XIIPhysics - Exemplar Problems Chapter 3. Current Electricity

Answer 1

use formula
R=rl/a
where R is resistance , r is resistivity , l is length of conductor, and a is cross section area .

RA/RB=(r^2-r'^2)/(rA)^2
=(1-1/4)/(1/2)^2=(3/4)/(1/4)=3/1
RA:RB=3:1