We made a circuit with a power supply at 3V DC, a bulb in parallel with a test material (metal/insulator/salt solution) and measured the Amps in the combined circuit, and in the test material branch.
I expected that the Amps in the bulb branch would remain the same regardless, since $I=V/R$, and $V$ and $R$ are constant in this experiment, and the overall amount of Amps would rise with better conductors tested.
With plastic as the test substance the overall current was $0.3$ A and the test branch was $0$ A with a bright bulb.
When we used saline, the overall was $0.3$ A and test branch was $0.1$ A with a bright bulb.
Using a copper strip, the overall was $5.9$ A and test branch was $5.8$ A with a dim bulb.
This means that the bulb branch went from $0.3$ A to $0.2$ A to $0.1$ A as the resistance on the test branch decreased.
Is it just a sketchy experiment or is there some aspect of physics I'm missing? I'm familiar with resistances in parallel and series and with Ohm's law.
Any input appreciated!!!