Three copper wires of lengths and cross sectional areas are (l , A) (2l, A/2) and (l/2 , 2A). Resistance is minimum in
Answer & explanation
Correct answer: option 3
Diameter is reduced to half, length increases 4 times as mass of material remains the same.
$ R = \rho \frac{l}{A} $
Resistance is minimum when length is minimum and area is maximum.