Eddy currents are loops of electrical currents induced inside conductors by a varying magnetic field in the conductor. The direction of this current is perpendicular to the magnetic field. The main characteristic of this current is, it only flows in closed loops.
Explanation of Eddy Current:
A magnet initiates round electric flows in a metal sheet traveling through its attractive field. See the below figure. It shows a metal sheet (C) moving to one side under a fixed magnet. The attractive field (B, green bolts) of the magnet’s north pole N goes down through the sheet. Since the metal is moving, the attractive motion through a given zone of the sheet is evolving. In the piece of the sheet moving under the main edge of the magnet (left side) the attractive field through a given point on the sheet is expanding as it gets closer to the magnet, dB/dt>0. From Faraday’s law of induction,
this makes a roundabout electric field in the sheet a counterclockwise way around the attractive field lines. This field instigates a counterclockwise progression of electric flow, in the sheet. This is the eddy current. In the piece of the sheet under the following edge of the magnet the attractive field through a given point on the sheet is diminishing as it is moving further away from the magnet, dB/dt>0, initiating a second vortex current a clockwise way in the sheet.
Another comparable method to comprehend the current is to see that the free charge transporters (electrons) in the metal sheet are moving with the sheet to one side, so the attractive field applies a sideways power on them because of the Lorentz power. Since the speed v of the charges is to one side and the attractive field B is coordinated down, from the correct hand rule the Lorentz power on sure charges F = q(v × B) is rearward of the outline (to one side when looking toward movement v). This causes a current I rearward under the magnet, which circles around through pieces of the sheet outside the attractive field, clockwise to one side and counterclockwise to one side, to the front of the magnet once more. The portable charge transporters in the metal, the electrons, really have a negative charge (q < 0) so their movement is inverse in course to the customary current that appeared.
The magnetic field of the magnet, following up on the electrons moving sideways under the magnet, at that point applies a Lorentz power coordinated to the back, inverse to the speed of the metal sheet. The electrons, in impact with the metal grid particles, move this power to the sheet, applying a drag power on the sheet corresponding to its speed. The dynamic energy which is devoured beating this drag power is dispersed as warmth by the flows moving through the opposition of the metal, so the metal gets heated under the magnet.
Because of Ampere’s circuital law, every one of the rounds flows in the sheet making a counter attractive field (blue bolts). Another approach to comprehend the drag power is to see that because of Lenz’s law the counter fields go against the change in the attractive field through the sheet. At the main edge of the magnet (left side) by the right-hand rule, the counterclockwise current makes an attractive field face-up, contradicting the magnet’s field, causing a terrible power between the sheet and the main edge of the magnet. Interestingly, at the following edge (right side), the clockwise current causes an attractive field pointed down, in a similar bearing as the magnet’s field, making an appealing power between the sheet and the following edge of the magnet. Both of these powers go against the movement of the sheet.
Applications of Eddy Current
- It is used in Electromagnetic braking.
- It is used in Repulsive effects and levitation.
- It is used to Identify metals.
- Eddy current used in Vibration and position sensing.
- This type of current also used in Structural testing.
- It is used in vending machines to detect coin.