Wires A as well as wire B are both made out of copper. Wire B is double as long as wire A. The diameter of wire B is doubles that of wire A.

Answer:

Resistivity is a characteristics of the material of which something is made-it doesn't depend on the size and shape of that something. Both wires are made of copper consequently they both have the same resistivity.

The bigger wire has features that tend to offset each other. The larger length by itself would give the wire a greater resistance as the charged particles have farther to go to make it through the wire. The larger diameter by itself would result in a smaller resistance as it means the passageway through which the charged particles flow is both wider and taller.

The confrontation is the resistivity times the ratio L/A of the length to the cross-sectional area of the wire. Doubling the length establish a factor of 2 into the numerator of that ratio. however the area is proportional to the square of the diameter thus doubling the diameter introduces a factor of 4 into the denominator of the ration. Thus doing both is equivalent to multiplying the expression for the resistance by 2/4. Therefore the resistance of the bigger wire is 1/2 that of the smaller wire.