What happens to the direction of eddy currents in a part when the electrical current in an eddy current coil reverses direction?

When the electrical current in an eddy current coil reverses direction, the eddy currents induced in the part also reverse direction. This phenomenon occurs due to the principles of electromagnetic induction as described by Faraday's law. When the current in the coil changes direction, the alternating magnetic field it produces also changes direction. This changing magnetic field induces eddy currents in the conductive material of the part, which react in accordance with Lenz's Law.

According to Lenz's Law, the direction of the induced eddy currents is such that they oppose the change in the magnetic field that produced them. Therefore, when the magnetic field switches direction due to the reversing current in the coil, the induced eddy currents will also switch direction in order to maintain this opposition to the change in magnetic flux. This is crucial for understanding the behavior of materials subjected to eddy current testing, as the performance and effectiveness of this non-destructive testing method rely heavily on the interaction between the alternating magnetic fields and the induced currents in the test material.

The other options do not accurately reflect the behavior of eddy currents in response to the change in current direction.