📌 Quick Answer
Eddy currents are circulating loops of electric current induced inside a conductor when it is exposed to a changing magnetic field.
They are produced by electromagnetic induction (Faraday’s law) and, by Lenz’s law, oppose the change that created them — useful for braking and heating but a source of energy loss in transformers.
🔹 Key Takeaways
- Eddy currents are induced circulating currents in a conductor in a changing magnetic field.
- They obey Faraday’s law (induction) and Lenz’s law (they oppose the change).
- Useful in induction heating, eddy-current brakes, metal detectors and testing.
- They cause heat losses in motors/transformers — reduced by using laminated cores.
What Are Eddy Currents?
Eddy currents are loops of electric current induced within conductors by a changing magnetic field, in accordance with Faraday’s law of electromagnetic induction. They flow in closed loops perpendicular to the magnetic field, much like swirling eddies in water — which is how they got their name.
Working Principle
When the magnetic flux through a conductor changes — because the field varies or the conductor moves — an EMF is induced. This EMF drives circulating currents inside the body of the conductor. By Lenz’s law, these eddy currents create their own magnetic field that opposes the original change, producing a retarding force and heat.
Applications of Eddy Currents
| Application | How eddy currents are used |
|---|---|
| Induction heating / furnaces | Eddy currents heat the metal directly |
| Eddy-current brakes | Opposing force slows trains and machines smoothly |
| Induction cooktops | Heat is generated inside the cooking vessel |
| Metal detectors & NDT | Detect flaws and metals by sensing eddy-current changes |
| Energy meters & speedometers | Provide damping and measurement |
Disadvantages and How to Reduce Them
In motors and transformers, eddy currents waste energy as heat (eddy-current losses). These losses are reduced by building the cores from thin, varnish-insulated laminations and by using high-resistivity silicon-steel, which break up the current loops.
Frequently Asked Questions
What are eddy currents?
Eddy currents are circulating electric currents induced in a conductor when it is placed in a changing magnetic field.
What law explains eddy currents?
They are explained by Faraday’s law of electromagnetic induction, and by Lenz’s law they oppose the change that produced them.
What are the applications of eddy currents?
Induction heating, eddy-current brakes, induction cooktops, metal detectors, non-destructive testing and instrument damping.
How are eddy current losses reduced?
By using laminated cores made of thin insulated sheets and high-resistivity silicon steel, which limit the size of the current loops.
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