Final answer:
Strain gauges are oriented at 45 degrees when measuring torsion to optimally detect shear strains, which are at their maximum due to twisting forces. This orientation ensures the most accurate readings for torsional deformation and makes torque balance measurements, which do not depend on g-values, reliable for measuring mass.
Step-by-step explanation:
Strain gauges are often oriented at 45 degrees when measuring torsion because this orientation allows for optimal detection of shear strains, which are at a maximum in materials subjected to torsional stress. In a torsion scenario, the material experiences strain variations due to twisting forces. Mounting strain gauges at 45 degrees to the axis of the applied torsion ensures that they are aligned with these directions of maximum strain, thereby providing the most accurate and sensitive readings for the measurement of torsional deformation.
It is significant that a torque balance used in measurements is independent of local variations in the acceleration due to gravity (g-values), unlike a spring balance. This makes the torque balance an effective method for measuring mass accurately, without being affected by such local variations. Therefore, when using strain gauges to measure torsion, their orientation is crucial to ensure precise measurements are obtained regardless of local g-values.