Three copper wires of length and cross-sectional areas are (L,A)`(2L,(A)/(2)),(L//2,2A)`, resistance is

Options

A. minimum in wire of cross-sectional area `(A)/(2)`
B. minimum in wire of cross-sectional area A
C. minimum in wire of cross-sectional area 2A
D. same in all three cases

Answer

C

Explanation

`l_(1)=L,A_(1)=A`
`l_(2)=2L, A_(2)=(A)/(2)`
`(R_(1))/(R_(2))=(l_(1))/(l_(2))xx(A_(2))/(A_(1)) implies R_(3) lt R_(1) lt R_(2)`