So, Billy has a Series Circuit that has [In Order] a Variable Resistor, Ammeter, Resistor, Voltmeter [Resistor and Voltmeter are Parallel] and Cell. How can you do an Investigation that has the Variable Resistor be your Changing Factor [You change that]

-So lets first Alter the Resistance of the Variable Resistor. This will Affect the Current flowing, and the Potential Difference. -Take a Few Readings from your Ammeter and Voltmeter as you Make the Changes to the Resistance. -Using this Data, you can make a I-V Graph and can also measure the Resistance on top With it -Watch out for the Temperature of the Circuit, as it will Affect the End Results. [and its generally Dangerous] If it gets too hot, Disconnect it and allow it to Cool Down. If you feel Uncertain about a Result, you can do a Repeat or an Average.