A cylindrical conductor of length `l` and uniform area of cross-section `A` has resistance `R`. Another conductor of length `2 l` and resistance `R` of the same material has area of cross-section :

Options

A. `A//2`
B. `3A//2`
C. `2A`
D. `3A`

Answer

C

Explanation

In first case,
Resistivity of the conductor, `p = (RA')/(l)` ....(i)
In second case,
Resistivity of the conductor, `p = (RA')/(2l)` ....(ii)
`because` For same material, resistivity of the conductor will be same.
So, on substituting the value of p in Eq. (ii), we have
`(RA)/(l) = (RA')/(2l) rArr A' = 2A`