Which of the following would normally be considered the best fill factor when testing straight tubing with an encircling or feedthrough coil?

The best fill factor when testing straight tubing with an encircling or feedthrough coil is considered to be 0.95 (95%). A fill factor is a measurement of how effectively the coil encompasses the test object—in this case, the straight tubing. A higher fill factor indicates that a larger portion of the tubing is being tested, thus increasing the sensitivity and reliability of the electromagnetic test.

A fill factor of 0.95 means that 95% of the coil's area is effectively utilized for induction, leading to better signal-to-noise ratios and more accurate detection of any flaws or inconsistencies within the tubing. This high fill factor optimally couples the magnetic field to the test object, ensuring that any defects will more likely be detected due to the enhanced interaction between the coil's magnetic field and the material.

In contrast, lower fill factors may lead to less effective testing because a smaller portion of the tubing will be analyzed, potentially allowing defects to go undetected. A fill factor of 0.50 (50%) significantly reduces the effectiveness of the coil in generating a usable electromagnetic field over the tubing. Similarly, fill factors of 1.75 (175%) and 0.25 (25%) indicate either an impractical scenario where