Depth of Penetration & Current Density
Eddy currents are closed loops of induced current circulating in planes perpendicular to the magnetic flux. They normally travel parallel to the coil's winding and flow is limited to the…
Impedance
Electrical Impedance (Z), is the total opposition that a circuit presents to alternating current. Impedance is measured in ohms and may include resistance (R), inductive reactance (XL), and capacitive reactance (XC). However, the total impedance is…
Circuits and Phase
A circuit can be thought of as a closed path in which current flows through the components that make up the circuit. The current (i) obeys Ohm's Law, which is…
Mutual Inductance
The magnetic flux through a circuit can be related to the current in that circuit and the currents in other nearby circuits, assuming that there are no nearby permanent magnets.…
Self-Inductance and Inductive Reactance
The property of self-inductance is a particular form of electromagnetic induction. Self inductance is defined as the induction of a voltage in a current-carrying wire when the current in the wire itself…
Induction and Inductance
Induction In 1824, Oersted discovered that current passing though a coil created a magnetic field capable of shifting a compass needle. Seven years later, Faraday and Henry discovered just the opposite. They noticed that…
Current Flow and Ohm’s Law
Ohm's law is the most important, basic law of electricity. It defines the relationship between the three fundamental electrical quantities: current, voltage, and resistance. When a voltage is applied to a circuit containing only resistive…
Properties of Electricity
Since eddy current inspection makes use of electromagnetic induction, it is important to know about the scientific principles of electricity and magnetism. For a review of these principles, the Science…
Basic Principles of Eddy Current Inspection
Eddy current inspection is one of several NDT methods that use the principal of “electromagnetism” as the basis for conducting examinations. Several other methods such as Remote Field Testing (RFT),…
History of Eddy Current Testing
Eddy current testing has its origins with Michael Faraday's discovery of electromagnetic induction in 1831. Faraday was a chemist in England during the early 1800's and is credited with the…
