How do I make a circuit that can find the resistance of different electrical conductors (Copper, Steel, Iron and Aluminium) - what sort of experiment would i have to conduct and how?
You need to use constant power supply with known current strength and a voltmeter. First, connect your conductor to power supply and measure the voltage on it's contacts. After that, you can calculate the conductor's resistance using the Ohm's law: R=U/I. This method will work if you have sufficiently powerful power supply that will not decrease current strength after connectioning the conductor.