Laws of Eddy Current and How are they Implied in Physics?

Eddy current in physics is also known as the Foucault current. Conductors that are triggered by a constantly changing magnetic field within them can generate eddy currents. In other words, eddy currents are closed loops of electric current induced by a changing magnetic field. Faraday’s law of induction forms the basis of Eddy Current. It states that a current will be induced in a conductor that is exposed to a changing magnetic field.

The Eddy Current Principle plays the role of Self-inductance. 

An AC electromagnet or transformer can create a time-varying magnetic field that induces eddy currents in the static conductors placed within a certain diameter. For example, an eddy current can be created using a magnet and a conductor by their relative motion.

Eddy Current Flow

In physics, the Law of Eddy Current states that it goes through the conductor in only closed loops. Another striking feature of this current is that it always works in a plane that is perpendicular to its magnetic field. 

Depending on the magnitude of the magnetic flux, circle area, the strength of the magnetic field, and, conversely, material resistivity, the magnitude of the circle’s current will vary, respectively.

Eddy Current’s Magnetic Field 

Eddy current flows where streams revolve continuously in circles around the conductors. These are triggered by changing the magnetic fields and developing them in closed rings that are vertically connected to the plane of the magnetic field, aka Eddy Current Magnet. The magnetic field enclosing a fixed channel can be varied when a conductor is moving across it, or when an eddy current flows in response to a movement within it.

Therefore, any change in the magnetic field’s intensity in the conductor translates to circling current flow. Magnetisation, round cross-sectional region, and current magnitude are all directly related to this current magnitude field. The rate of the conductor’s resistivity is inversely related to them. This is the fundamental Law of Eddy Current in physics.
According to Lenz’s Law, an eddy current induces a magnetic field that flows against the change in the magnetic field that caused it. As a result, the current goes back to the originating magnetic field. 

For example, the moving magnetic field will cause an eddy current to be a part of the conductive surface, causing a dragging impact on the moving magnet.

Implications

Eddy current has an extensive impact on many applications in our day-to-day lives. The implication of eddy current in physics are listed below-

1. Train Brakes
   As brakes are applied to a train, its wheels are exposed to a magnetic field, which produces eddy currents. Eddy currents and the applied field interact magnetically to slow down the wheels. The impact is larger as the wheels spin faster; therefore, as the train slows, the braking force is reduced, resulting in a smooth stop.
2. Electromagnetic damping
   Galvanometers with deadbeats are made with the material having high resistivity. Before coming to a complete stop, the needle usually oscillates a little around its equilibrium point. This creates a delay in getting the reading. Thus, the coil is wound across a non-magnetic metallic frame to avoid this. Eddy currents form in the metallic frame as the coil is deflected, bringing the needle to a near-instant stop.

As a result, the “coil’s” motion is slowed. A fixed core constructed of non-magnetic metallic material is used in some galvanometers. Coils oscillate and are brought to a halt by eddy currents in the core.

1. Electric Power Metres
   Eddy currents cause the electric power metre’s gleaming metal disc to rotate. The electric currents in the disc are induced by the magnetic field. You can also see the gleaming disc in your own home.
2. Induction Furnaces
   Due to the large electromotive force created, huge eddy currents form in rapidly changing magnetic fields. There is a rise in temperature as heat is generated by eddy currents. Large amounts of heat generated causes a high elevation of temperature. Therefore, a coil is wound over the constituent metal, which is put in a rapidly oscillating magnetic field created by a high-frequency source. The metal easily melts by the heat generated. This is how metals are extracted from ores. An induction furnace can be used to make alloys by melting metals at a very high temperature.
3. Speedometers
   These currents are utilised to determine the speed of any vehicle. A speedometer is made up of a magnet that rotates in response to the speed of our car. Eddy currents are created in the drum. The pointer attached to the drum indicates the vehicle’s speed as it rotates in the rotating magnet’s direction.

Conclusion

Eddy currents are currents that circulate in conductors like swirling whirls in a stream. Changes in magnetic fields cause them to flow in closed loops, perpendicular to the magnetic field plane. Eddy current is generated when a changing magnetic field surrounds a conductor. For instance, when a moving conductor passes through a magnetic field or when a stationary conductor moves through a magnetic field. So, anything that affects the intensity or direction of a magnetic field can result in eddy currents. A magnetic field, loop area, and the rate of change of magnetic flux determine its magnitude and size; and the conductivity inversely determines its size.

Like any other current flowing through a conductor, an eddy current produces a magnetic field. According to Lenz’s Law, the magnetic field produced by a magnetically induced current, such as an eddy current, will oppose the change in the originating magnetic field.