Eddy currents

An eddy current is a circular current induced in a material by a changing magnetic field produced by a solenoid. This is used to test materials by moving a small solenoid over the surface of a material, if there is a discontinuity in the material creates a decrease in the current because the path of the eddy current is longer because it has to extend around the break in material. The smaller the solenoid the smaller the defects it can detect because the eddy currents are more condensed.



Eddy current testing can use very small solenoids to detect surface imperfection, it an also use medium sized solenoids to be fed down the center of pipes, or the use of a larger solenoid may be used at a manufacturing facility the runs the material through the center of the solenoid to detect lateral discontinuities in the materials.