Eddy Current Overview
An eddy current is a current that occurs in an exceeding conductor as a result of a changing magnetic field. They flow in tight loops perpendicular to the magnetic field in an extremely planar manner. According to Lenz's law, this current swirls in such a manner that a magnetic field opposing the change is produced; for this to occur in an exceedingly conducting medium, electrons swirl on an excessive plane perpendicular to the magnetic field.
Eddy Current Definition
An eddy current is a current that forms in a conductor as a result of a changing magnetic field. They move in tight loops perpendicular to the magnetic field. Eddy currents (also known as Foucault's currents). According to Lenz's law, the current swirls in such a manner that a magnetic field opposing the change is created. For this to happen in a conductor, electrons must swirl in a plane perpendicular to the magnetic field. Eddy currents create a loss of energy because of their inclination to resist. Eddy currents convert more usable kinds of energy, such as kinetic energy, into heat, which is inherently inefficient.
Read more about the SI Unit of Electric Current and the Magnetic Effects of Electric Current.
Origin of the Eddy Current
Eddy currents are named after comparable currents found in water in fluid dynamics, which cause localized zones of turbulence known as eddies and give birth to persistent vortices. Eddy currents, meanwhile, might take a while to build up and only last for a brief time in conductors due to their inductance.
History of the Eddy Current
François Arago(1786-1853), the 25th Prime Minister of France and a mathematician, physicist, and astronomer, was the first to observe eddy currents. In 1824, he discovered what is now known as rotatory magnetism, as well as the ability of most conductive things to be magnetized; these findings were developed and explained by Michael Faraday (1791-1867). Eddy currents generate a secondary field, which cancels out a portion of the external field and causes some of the external flux to avoid the conductor.
Read more about the Faraday Constant and What is Lorentz Force?
Properties of Eddy Current
The following are the properties of an eddy's current-
- Defects like fractures, corrosion, sharp edges, and so forth distort them.
- Eddy current intensity increases at the surface and diminishes with depth.
- These can only be found in conducting materials.
Eddy Current Applications
To comprehend what eddy current is, one must first comprehend Faraday's electromagnetic induction. Large eddy currents are produced in rapidly changing magnetic fields due to the creation of heavy emf. As a result of the high temperature, eddy currents can generate heat. A coil over a component metal put in a highly oscillating magnetic field will therefore create a high-frequency alternating current (AC). The temperature produced by a strong eddy current is high enough to melt the metal. This is employed in the extraction of metals from ores. The following table gives details about the uses of eddy currents-
|
Uses |
Description |
|
Alternating Current (AC) Induction Motors |
- |
|
Applications for Data Processing |
Non-destructive eddy current testing is used to analyze the composition and durability of metal structures. |
|
Automobile Speedometers |
Eddy currents are employed to determine a vehicle's speed. A speedometer is made out of a spinning magnet that rotates in response to the vehicle's speed, causing an eddy current in the drum. When the drum rotates in the direction of the revolving magnet, the connected pointer displays the vehicle's speed. |
|
Electric saw or drill for emergency stoppage |
Eddy current is also utilized in electrical saws and drills for the emergency stoppage. |
|
Energy Meters |
Eddy currents cause a metal disc in an electric power meter to revolve. By alternating different currents in a coil, the magnetic field causes electric currents in the disc. |
|
Free-fall devices (detecting coins in vending machines) |
Eddy current assists in the detection of counterfeit coins and notes in vending machines using free-fall devices. As the coins pass by a stationary magnet, eddy currents slow them down. |
|
Galvanometers (instruments that measure tiny electrical currents) |
An oscillating coil creates an eddy current in the galvanometer, and its resistive forces oppose additional coil oscillations. As a result, the coil can quickly reach its equilibrium position. |
|
Hyperthermia Cancer Treatment |
During hyperthermia cancer therapy, eddy current heating is employed to heat the tissue. Eddy currents in the conducting tubings are generated by proximal wire windings attached to a capacitor to form a tank circuit that is connected to a radio frequency source. |
|
Induction furnaces |
Eddy current is utilized to boost temperatures uniformly in induction furnaces. Due to the enormous emf created, massive eddy currents begin to flow in quickly changing magnetic fields. This results in high temperatures. |
|
Magnetic Brakes |
When you apply the brakes, the metal wheels are exposed to a magnetic field, which causes eddy currents to flow through them. The interplay of the eddy currents and the applied magnetic field causes the wheels to slow down. |
|
Sensors for proximity and displacement |
- |
|
Electromagnetic Damping |
It is used to make deadbeat galvanometers. Before settling, the needle frequently oscillates slightly around its equilibrium position. To avoid the delay in reading acquisition caused by this, the coil is looped around a non-magnetic metallic frame. Eddy currents occur in the metallic frame as the coil is deflected, causing the needle to come to rest relatively quickly. As a result, the "coil is dampened" in its movement. |
Why is Eddy Currents ineffective?
When an alternating current runs through a wire, much of the current is really flowing at the wire's surface. This is known as the skin effect, but it is really created by eddy currents. The current in an alternating current wire alternate back and forth. This, of course, means that the magnetic fields formed by that current are changing. This causes eddy currents to form within the wire, obstructing the passage of electricity. One could obtain greater current through a given wire if eddy currents did not exist. Consider a transformer as another example. Eddy currents are responsible for the heating of a transformer's steel core.
Points to Remember
- According to Lenz's law, this current swirls in such a manner that a magnetic field opposing the change is produced; for this to occur in an exceeding conductor, electrons swirl on an excessive plane perpendicular to the magnetic field.
- An eddy current is a current that occurs in an exceeding conductor as a result of a changing magnetic field.
- A speed indicator is made out of a magnet that rotates in response to the speed of our car.
- The speed of the vehicle is shown by the pointer attached to the drum as it rotates in the direction of the magnetic magnet.
- These currents are utilized to determine the speed of any vehicle.
- They flow in tight loops perpendicular to the magnetic field in an extremely planar.
- This effect was discovered by physicist Foucault between 1819 and 1868, and these currents are known as eddy currents.
- Within the drum, eddy currents are created.
Sample Questions for Eddy's Current
Sample Question 1: Which of the following laws applies after eddy currents are formed or produced?
- Lenz's Law
- Gauss's Law
- Both A and B
- None of the above
Solution- Len'z Law is the correct answer.
Sample Question 2: Once a very metal-like conductor is formed, eddy currents are produced through-
- The magnetic flux associated with it shifts.
- It is situated within a dynamic magnetic field.
- Located within a magnetic field
- A and B both
Solution- D is the right answer because they are formed when the magnetic flux traveling through the metal item changes continually. This might happen for a variety of reasons. 1. the item is located in an area with a dynamic magnetic field, and the item goes in and out of the magnetic field area constantly.
Sample Question 3: Which of the following does not use the application of eddy currents?
- Furnaces for Induction
- LED Lighting
- Electricity meters
- Magnetic train breaks
Solution- LED Lighting is the right answer.
Sample Question 4: Use of induction furnaces
- mutual induction
- self-induction
- eddy currents
- none of the A, B and C
Solution- eddy currents is the right answer
Sample Question 5: Where does eddy current travel?
- parallel to the test surface
- in closed spaces
- Materials that are not conductors
- All of the above
Solution- B is the right answer.