ElectricityWatch this thread
Just to check, is the idea of having a variable resistor to create a potential divider circuit that'll allow different voltages and current to be measured. Another question is this only works when the diode has resistance. If the diode had negligible resistance then it would act as a wire and would't have a pd across it?
However, both circuits enable you to vary the current through the diode. So both were accepted.
The diode doesn't have zero or negligible resistance - this is what the graph shows. At point A on the graph its resistance R = V/I
If the diode had negligible resistance you would need a resistor (or variable resistor) in the circuit to limit the current.
The diode will always have a pd across it, even if that pd is very small.