Because a magnitude, in any direction, can be expressed as the sum of two orthogonal magnitude components, aligned with the sides of the four electrode square.Dario56 said:Why is it that resistances are measured specifically in mutually orthogonal directions?
Hmm, well resistivity isn't a vector, so that the values of resistivity in both directions are equal to the vector components in both directionsBaluncore said:Because a magnitude, in any direction, can be expressed as the sum of two orthogonal magnitude components, aligned with the sides of the four electrode square.
In effect, it is doing a polar to rectangular conversion.
My question is much simpler than you imagine.Dullard said:If I understand your question:
The Van der Pauw method is a technique used to measure the sheet resistance and Hall coefficient of thin films. It is widely used in materials science to evaluate the electrical properties of materials, particularly in the context of semiconductors and thin metallic films.
The Van der Pauw method involves placing four contacts on the perimeter of a thin, flat, and ideally isotropic sample. By passing a current through two opposite contacts and measuring the voltage across the other two, and then repeating the measurement with different pairs of contacts, one can calculate the sheet resistance using the resistivity formula derived by Van der Pauw. The symmetry of the setup allows for an average measurement that minimizes errors due to sample geometry.
The sample must be flat, relatively thin, and approximately homogeneous in thickness and material properties. It should also have an arbitrary shape but must be simply connected (no holes). The contacts must be placed on the perimeter of the sample. These requirements ensure accurate and reliable measurements of the electrical properties of the material.
Yes, the Van der Pauw method can measure both the sheet resistance (and thus resistivity, if thickness is known) and the Hall coefficient. By applying a perpendicular magnetic field to the sample during the measurement, one can also obtain the Hall voltage, which is used to calculate the Hall coefficient. This dual capability makes the method particularly valuable for characterizing semiconductor materials.
One of the primary limitations of the Van der Pauw method is that it requires the sample to be isotropic and homogeneous in terms of its electrical properties, which is not always the case in practical materials. Additionally, the accuracy of the method can be affected by the placement and quality of the contacts. Imperfections in sample geometry or anisotropy in material properties can also lead to errors in the measurements.