Task: Thin Manganin wire of the length l = 0.5 m is glued to the electrically insulating rod. The insulating rod is subsequently stretched by applying axial mechanical force. Prior to stretching the resistance of Manganin wire was R0 = 10 ? and after applying the axial force R1 = 10.01 ?.

Determine:

a) diameter of the wire D when no mechanical force is applied;

b) relative length change of the insulating rod Δl / l [%]

Note:

1) Assume no relative movement between the wire and insulating rod;

2) Electrical resistivity change due to stretching can be neglected;

3) Relative deformations in axial and transverse dimensions of the wire are satisfying the Poisson's ratio which is µ=0.35.

4) Electrical resistivity of Manganin is ρ = 43·10-8 ?m.