Contact resistance

We were doing an experiment to find the EMF and internal resistance of a cell by clipping in different sizes of resistor. The idea is that the resistance changes the current and the current heats the internal resistance, changing the output p.d. If you plot output p.d.against current, the y-intercept is the EMF and the internal resistance is - gradient. But with the 1 Ohm resistor I was asked if the direction of the resistor affected the current like it would with a diode.

The answer is that it doesn't, but that there is extra resistance added into the circuit by the way that the clips grip the wire. It is unavoidable and changes in size every time you reattach, hence the seemingly different reading. It is a small resistance but might be a reasonable fraction of 1 Ohm and thus affect the current readings for very small resistances.