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Eddy currents are swirling currents of electricity that circulate within conductive materials when they are exposed to changing magnetic fields. Imagine a tiny whirlpool of electricity dancing through a metal sheet when a magnet moves nearby. These currents are not something we can see with our naked eyes, but they sure do exist. To understand the concept better, let us break it down. When a magnetic field changes near a conductive material like metal, it induces an electric current within that material. This current then creates its own magnetic field, which opposes the original change in the magnetic field that induced it. It’s like a game of tug-of-war between magnets, but with electricity involved! In this blog, let us get to know what is Eddy Current along with its usage to us.
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What is Eddy Current?
The name “eddy” comes from their resemblance to whirlpools or eddies in a stream. Eddy currents are named because of the current’s eddy-like appearance. These currents were first described by French physicist Léon Foucault in 1855.
Foucault’s definition emphasizes the dynamic nature of these currents and their relationship to magnetic field variations. Foucault’s experiments focused on the specific phenomenon of these induced currents flowing in closed loops within the conductor itself, rather than in an external circuit. Thus, eddy currents are also known as Foucault’s currents.
Definition of Eddy Currents: Eddy currents are circulating electric currents induced within a conductor by a changing magnetic field.
These currents flow in closed loops within the conductor, resembling whirlpools or eddies in a stream. They arise because the changing magnetic field disrupts the motion of electrons in the conductor, causing them to move in circular paths.
However, The concept of what is eddy currents likely stemmed from the well-established principle of electromagnetic induction, which was discovered by Michael Faraday in 1831.
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Eddy current refers to an induced current that is generated in a conducting coil as a result of a change in the magnetic flux. According to Faraday’s laws of induction, eddy currents flow in closed loops and in planes that are perpendicular to a magnetic field. When an electromagnet is connected to a battery, it will generate a current in a magnetic field. This current will also induce an eddy current on a magnetic plate. The induced current will take the form of an eddy in the plate. It is also called “eddy currents” because they form in the shape of whirlpools or in the shape of eddies in water.
Eddy current is present in every solid and is one of the basic properties of solid conducting bodies. When the magnetic flux of a conductor changes, the free electrons in the conductor become subject to a sudden magnetic force. This force causes the free electrons to move in the form of small eddies.
Here’s a breakdown of the key factors that influence eddy currents:
- Changing Magnetic Field: A constant magnetic field won’t induce eddy currents. The magnetic field needs to fluctuate in strength or direction for them to appear.
- Conductivity: Good conductors like metals allow for easier movement of electrons, leading to stronger eddy currents.
- Material Thickness: Thicker conductors generally experience greater eddy current losses due to the larger volume of material affected by the changing magnetic field.
Faraday’s Law of Induction
Magnetic induction was first discovered by Michael Faraday, an English physicist, in the year 1830. Faraday gave a law that describes how an electric current creates a magnetic field, and how the changes in the magnetic field produce a magnetic current and generate an electric current in a conductor.
To understand Faraday’s law of induction, you first need to know about magnetic fields. When you compare magnetic fields to electric fields, you will find that magnetic fields are more complicated. Magnetic poles are always pairs. Magnets have two poles, the north pole and the south pole. Faraday’s law of induction states that a changing magnetic field can induce an electromotive force (EMF) in a conductor, which can then drive electric current.
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Eddy Current Application
There are various important applications of Eddy Currents in our day-to-day life. Since these currents have the property of heating, they can be used in numerous ways. Some of them are –
- Train Brakes: Modern trains often utilise eddy current braking systems. Electromagnets positioned near the wheels generate a changing magnetic field. This, in turn, induces eddy currents within the metallic wheels, opposing their rotation and creating a drag force that slows down the train.
- Induction Cooktops: The convenience of induction cooktops relies on the power of these currents. A rapidly alternating magnetic field beneath the cooking surface induces currents directly within the cookware. This internal heating allows for efficient and precise temperature control.
- Security Systems: These currents are at play in some anti-theft tags. These tags contain a thin metal strip that disrupts the changing magnetic field generated by a security sensor at store exits. The altered magnetic field triggers an alarm if an un-deactivated tag passes through.
- Wireless Charging: The wireless chargers used for smartphones and other devices often employ the principle of eddy currents. A coil in the charging pad generates a changing magnetic field that induces currents within a receiving coil embedded in the device, transferring energy for wireless charging.
- Microwaves: While not the primary heating mechanism, the currents can contribute to heating food unevenly in a microwave. The metal components of packaging or certain utensils can experience eddy currents, creating localised hot spots within the food.
Questions with Answers on Eddy Currents
For example, if an eddy current (I) of the size I pass through a core path (r) of resistance, it will lose energy as heat according to the following power equation: Power = I2R Since this is a waste of energy, it is classified as eddy current loss (sometimes called iron loss).
Hysteresis loss depends on the reversal of magnetism in a magnetic material, whereas interactions between the conductor and magnetic field cause eddy current loss.
Eddy Current is an electric current caused by an alternating magnetic field.
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Hope this blog helps you understand what is Eddy Current. Keep reading more of our blogs to learn about the basic concepts of Physics!