Resistance of a wire

What effects the resistance of a wire?

We are going to conduct an experiment to find out the resistance of a wire by changing some variables.
These include:

* Length of wire
* Material used for wire
* Gauge of wire
While we conduct the experiment to find out which if any of these variables affects the resistance of wire, we will have to keep some things the same to make the tests valid. The things we won't differ will be, the same equipment (because some of the power packs may give out more voltage than another), the current which will be 0.5A (to stop the wire heating and therefore the resistance would change), and for the same reason we won't change the temperature.

Once the experiment is set up it will look like this.

Prediction
I predict that the longer i make the piece of wire, the higher the resistance will be, because the free electrons will have more metal ions to collide with, so less of them will diffuse at the en...