What principle allows for testing with similar geometry under cylindrical or spherical symmetry?

The principle that allows for testing with similar geometry under cylindrical or spherical symmetry is the Similarity Law. This law is based on the concept that certain systems can be modeled or analyzed by examining geometrically similar configurations, where the relationships between physical quantities are preserved regardless of the scale of the system.

In the context of non-destructive testing methods, like eddy current testing, the Similarity Law allows testers to ensure that measurements taken on a small-scale model or a different configuration can be interpreted in the same way as if they were taken on the actual part being evaluated. This is particularly important in materials testing, where different shapes and sizes may respond in similar ways when subjected to certain conditions, thus allowing for effective analysis without having to test every variation individually.

Other principles such as Ohm's Law, Kirchhoff's Law, and Newton's Third Law do not specifically address geometric similarity in the context of testing under cylindrical or spherical configurations, making the Similarity Law the appropriate choice for this question.