A copper wire has a resistance of 0.5ohm. Another copper wire of the same mass as the first one is double in length of the first. Find the resistance of the second wire

Both the wires have same mass and also they are of the same material. So, their density is same and hence their volume will also be same.

Let ρ be the resistivity of the material of the wire.

First wire:

Length = L

Area of cross-section = A

Resistance, R = ρL/A

Second wire:

Length = 2L

Area of cross-section = A^/

Since, volume of the wires are same.

Volume = AL = A^/(2L)

=> A^/ = A/2

So, the resistance of the second wire is,

R^/ = ρ(2L)/(A/2) = 4R = 4 × 0.5 = 2 Ω