Acopper wire is stretched so that its length increases and its diameter decreases. as a result:
a. the wire's resistance decreases, but its resistivity stays the same.
b. the wire's resistivity decreases, but its resistance stays the same.
c. the wire's resistance increases, but its resistivity stays the same.
d. the wire's resistivity increases, but its resistance stays the same.

A) False; B) False; C) True; D) False

Explanation: In order to explain this problem we have to take into account the expresion of the resistence of the condutor wire, which os given by:

R=ρ*L/A where ρ, L and A are the resistivity, length and area of the conductor.

As it can be seen, the resitence is inverse to the area so when the diameter decrease the resistance should increase its value. (A, C).

The resistivity does not depend on the length or diameter of the wire, only it depends on the material use to made the wire.  (B,C and D).

the answer would be 32*f

the higher the current the higher the mag field around it the higher the influence on the compass