A change in the f/fg ratio will result in what?

The correct answer involves understanding the relationship between the frequency of the applied alternating current (AC) and the frequency of the generated eddy currents in Eddy Current Testing (ET). The f/fg ratio is a significant parameter, where 'f' refers to the frequency of the excitation signal and 'fg' is the frequency at which the eddy currents naturally oscillate in the test material.

When there is a change in the f/fg ratio, it directly affects both the magnitude and the phase of the voltage across the coil. This happens because variations in the frequency of the excitation signal alter the inductive reactance of the coil, thereby impacting how effectively the coil couples to the induced eddy currents.

An increase in frequency can lead to a decrease in the magnitude of induced eddy currents, affecting the voltage amplitude across the coil. Simultaneously, this change in frequency can shift the phase relationship between the excitation voltage and the current in the coil. Therefore, both the magnitude of the voltage and its phase are influenced when there is a variation in the f/fg ratio, leading to the conclusion that both aspects are affected by this change.