The impedance of an eddy current test coil will increase if the:

The impedance of an eddy current test coil is influenced by the properties of the coil and the frequency of the applied current. As the test frequency increases, the inductive reactance of the coil also increases. Inductive reactance is directly proportional to frequency, described by the formula (X_L = 2\pi f L), where (X_L) is the inductive reactance, (f) is the frequency, and (L) is the inductance of the coil.

When the frequency rises, the alternating current encounters more resistance to change due to the increased reactive component, which raises the overall impedance. Since impedance in an alternating current circuit is the combination of resistance and reactive components, this increase in inductive reactance leads to an overall increase in the coil's impedance.

Understanding this relationship is crucial for effective eddy current testing, as the test frequency is a key parameter that helps optimize the detection of defects by influencing the depth of penetration and sensitivity of the testing process.