Possible source of error in this lab?

[Suy]

Homework Statement

http://img245.imageshack.us/img245/7259/12214351.jpg

Homework Equations

The Attempt at a Solution

I have no idea,
the previous lab i put gravity depend on location, but the teacher marked me wrong
If anyone can give me some hints, and i need 3...
I don't know if this 2 are right
electrical resistance
temperature
ty!

 

[ideasrule]

Well, Laura can't exactly make the magnetic field disappear for the wire outside the 0.025 m section she's considering. The ammeter is also going to be inexact. There might also be some problems with the magnet's field being non-uniform, but unfortunately we don't know what exactly she's trying to measure here.

 

[Suy]

ty for replying!
i have the data,
http://img49.imageshack.us/img49/7951/19681882.jpg