<< Deletion by Moderator >> My question concerns resistance-current characteristic. The investigation was aimed at measuring current at different potential differences, before the filament lamp started to shine and when it was shining so as to observe both ohmic and non-ohmic behaviour. Also after calculating the resistance, the characterisitc between it and current was to be analyzed. Anyway, the ammeter, voltmeter, filament lamp, wires and clips were used. Hence, my question is arising, do you have any ideas (except internal resistances), what could cause occuring of some errors (systematic or random) and how it could be improved ?