When measuring the I-V characteristic of a metal wire/diode/filament light bulb , what is generally the best circuit set up?
Change the voltage across the component directly using a variable power supply
Use a variable resistor to change the voltage across the component.
Use a potential divider set up to vary the voltage.
In all three cases, you have the voltmeter in parallel with the component and an ammeter in series. You'd have to make adjustments depending on the circuit (e.g. adding extra resistors in series) but as far as I understand, that's the basic setup.
My question is, in 2 and 3 are you not changing the resistance of the whole circuit when you're adjusting the voltage so you're actually changing the current measured by the ammeter indirectly? Is the effect so insignificant that it is ignored? Does this affect the I-V characteristic obtained?
In my view, I think 1 is the best setup for getting the I-V characteristic of a component as you're changing one variable only (which is voltage). Though I'm not sure if I understand the topic correctly.