If the conductivity of a test part in an eddy current test coil decreases, the magnitude of the eddy currents at a given depth in the test specimen:

When the conductivity of a test part decreases, the resistance to the flow of eddy currents increases. This situation impacts the generation and flow of eddy currents induced by the alternating magnetic field of the test coil. Eddy currents are generated in conductive materials in response to changing magnetic fields, and their magnitude is directly influenced by the material's conductivity.

As conductivity decreases, there is an increase in resistivity, which leads to a reduction in the magnitude of the eddy currents at any given depth within the test specimen. This relationship between conductivity and eddy current magnitude is fundamental in nondestructive testing principles. Therefore, as the conductivity drops, the eddy currents cannot circulate as freely or as strongly, resulting in a decrease in their magnitude. This relationship is crucial for interpreting test results in eddy current testing.