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 discussed on the page on current flow. The simple circuit below consists of a voltage source (in this case an alternating current voltage source) and…
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. Consider the following two circuits. The magnetic field produced by circuit 1 will intersect the wire in circuit 2 and create current flow. The induced…
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 is changing. In the case of self-inductance, the magnetic field created by a changing current in the circuit itself induces a voltage in the same…
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 a moving magnetic field would induce current in an electrical conductor. This process of generating electrical current in a conductor by placing the conductor in…
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 elements (i.e. no coils), current flows according to Ohm’s Law, which is shown below. I = V / R Where: I = Electrical Current…
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 of NDT materials on this Internet site may be helpful. A review of the key parameters will be provided here. Electricity It is well known…
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), Flux Leakage and Barkhausen Noise also use this principle. Eddy currents are created through a process called electromagnetic induction. When alternating current is applied to the conductor,…
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 discovery of electromagnetic induction, electromagnetic rotations, the magneto-optical effect, diamagnetism, and other phenomena. In 1879, another scientist named Hughes recorded changes in the properties of…
Eddy current testing a modern Non-destructive testing – NDT method that has become one of the prime tool for quality control of products, materials and structures at various stages of manufacturing and in-service inspections. Eddy current inspection can be used to find finest surface and subsurface flaws in any conductive material. Spectrums of quality control…
Acoustic emission is a very versatile, non-invasive way to gather information about a material or structure. Acoustic Emission testing (AET) is be applied to inspect and monitor pipelines, pressure vessels, storage tanks, bridges, aircraft, and bucket trucks, and a variety of composite and ceramic components. It is also used in process control applications such as monitoring…