Take the current reading then turn off the power and start again. Take four readings like this so that an average resistance can be found. Next, change the thickness of the wire and do the experiment again. Use the diameters 0.71mm, 0.56mm, 0.28 mm and 0.20mm. Although the diameters haven t the same interval between them, once we have worked out the resistance, we can draw a graph to discover any relationship between the thickness and the resistance of wire.
Resistance is caused by electrons bumping into ions.
If the length of the wire doubles, the electrons bump into the ions twice as much so the resistance will double.