Eddy Currents

Introduction

In this article, you will find all the important concepts related to Eddy currents. This article will also help you understand the basics of Eddy currents, a few examples of eddy currents, some disadvantages of eddy currents, and practical applications as well to help you solve your textbook questions.

Let us start with defining what Eddy currents are.

What are Eddy currents?

Eddy currents refer to the currents that get produced in a conductor when it is subjected to varying magnetic flux. Eddy currents are also called Foucault currents by the name of the scientist Foucault. Eddy currents are given their name because they have a similar pattern to eddies in the water.

If we take an electromagnet that is linked with a battery, the magnetic field will be induced as a result of the current, inducing current in the metallic plate. The current flowing will flow in the form of eddies making the metallic plate drift in the air because of eddy currents. Mathematically it is calculated as: 

i = (induced emf)/(Resistance of the conductor)

i =(e/R)

e = -(dΦ/dt)

Hence, i=-(dΦ/dt)/R

The direction and magnetic properties will be the same as the produced current in the case of electromagnetic induction.

What are some examples of Eddy currents?

1. Metal plate: In deprivation of magnetic field: there is no damping. 

In the case of a metal plate, which is suspended with the help of a thread freely. As there is no magnetic field, the plate will continue oscillating with no damping.

• Metal plate: In the existence of a magnetic field: there is damping happening.

If the magnetic field exists, it oscillates but it is discontinuous after some time because of the existence of damping. As the plate continues on, it enters the magnetic plate and leaves it. When it enters the area of a magnetic field there is a rise in the region. It results in changes in the flux. As flux varies, there is produced current. The direction of the produced current will oppose its motion. When the metal plate leaves the magnetic field, again current will be produced but in the opposite direction. The effect of produced currents together gives the effect of eddy currents. Because of the produced current, the motion is damped as they are opposite to the motion of the plate.

• Metal plate with slots: In presence of magnetic field: Damping reduced.
• When the plate varies the damping is lessened as there is a reduced region. The eddy currents are reduced as a result damping is lessened. Eddy currents are opposite to the motion of the plate and as they are lessened, the damping is lessened.

What are the disadvantages of using Eddy currents?

1. There exists a leakage of magnetic flux.
2. There is an extreme heating of the metallic cores of electric motors, transformers, and other devices of such a kind. 
3. To avoid the extreme heating of the metallic cores, the metallic sheets are kept in the form of very thin sheets that are electrically insulated. The cores are insulated with an insulating material to avoid the transfer of heat in its surroundings. Such cores are called laminated cores.

What are the practical Applications of Eddy currents?

1. Electromagnetic brakes – Eddy currents are used to control the speed of fast electric trains. In the cases of electric trains, magnets are kept on the tracks so that currents are produced on the wheels of the electric train. There is no need for maintenance of electromagnetic brakes and can easily replace friction brakes.

 Electromagnetic damping – Electromagnetic damping in galvanometers helps to lessen the variance around the positions of equilibrium. Galvanometers are instruments which assist in measuring currents.

Conclusion

Eddy currents refer to the currents that get produced in a conductor when it is subjected to varying magnetic flux.  Eddy currents are used to control the speed of fast electric trains. In the cases of electric trains, magnets are kept on the tracks so that currents are produced on the wheels of the electric train. Eddy currents have a tendency to always oppose the relative motion. They are the same eddies as a result of the movement that keeps going and the direction of the current keeps varying depending on the variation in flux. Looking like eddies in the water. The eddy currents also result in damping as they oppose the motion. Eddy currents are induced in the copper plate, while they enter and leave the area of the magnetic field. Cutting slots in the copper plate lessens the effect of Eddy currents.