What Factors Affect the Current Flowing Through a Wire?

I am going to investigate how the resistance of the wire affects a current flowing through a wire. I know that as resistance changes, current changes, as Ohm's law:
I = V/R. If one part of an equation changes, the equal must be done to the opposite side. To detect how resistance affects current, I must first discover what factors affect resistance. These factors are:

· Length of the wire – if a wire is longer; there are more particles for electrons to move through, and therefore more resistance.
· Conductivity – depending on the metal of which the wire is made there will be less/more resistance.
· Temperature – many metals' resistance changes as temperature increases, that is why we use constantan wires.
· Diameter/Cross sectional area – if a wire has a larger diameter, then the particles have more room to flow.

I shall investigate what affect the diameter of a wire has on its resistance, and consequentially the current of the circuit. I shall keep the other variables constant, to ensure this is a fair test.

For this investigation, I will need the following apparatus:
· Power pack
· Variable resistor
· Ammeter
· Voltmeter
· 6 wires of different diameters

I will set up a circuit as in the diagram:

By running a constant voltage through the wire, I will be able discover the resistance of it with Ohms law, because of the constant voltage, and the fact I will know the resistance of the circuit using the variable resistor. I will maintain a constant, low voltage output from the power pack, so the voltage is not too high to be read by the voltmeter. I will connect the first wire, then run the pre determined voltage through it, waiting a short time until the ammeter has rested upon one result, and then record that result. I shall take 7 readings, each following the same procedure as the first, each of which will be of a different wire diameter. I will be using the following 7 wire sizes:

To ensure that these are in fact the correct diameters, as