Resistivity measurements with samples in the form of a double cross

Abstract

Samples in the shape of a double cross are analyzed, both theoretically and rheographically, as to their suitability for resistivity measurements. It is found, provided certain geometrical limitations are observed, that the presence of lateral arms instead of true point contacts has very little effect on the resistance observed. Typically, the voltage measured between the ends of lateral arms with half the cross section of the main sample body and separated by eight sample widths, is only 1% less than the voltage between two point contacts of similar separation placed on the main sample body. For known dimensions the effect of the side arms is calculated rigorously. Excellent agreement is found with measurements. The rheographic experiments also show that current and voltage arms need only be two or three times as long as they are wide to ensure the validity of the calculation.